From 39856b8e91e69ac7b3a905e1cb591f81bbbcad88 Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Wed, 25 Jun 2014 19:32:49 +0100
Subject: [PATCH 01/11] added binary search for collections

Added `search` method to collection prototype. automatically used by
`where` and `findWhere` when it is possible to do so.

user may provide:
- a comparison function (comparator unused)
- a value to search for (the value of the model[comparator] sought -
requires comparator to be a string)
- a model to search for (where `comparator` is a function)

Users may also request that it is the index of the model that is
returned or that the model of highest/lowest index which matches the
comparison is sought.

One point that may need to be considered is that the behaviour when a
model is input as `toFind` but the `comparator` is a string is different
from that when `comparator` is a function.
---
 backbone.js        | 73 +++++++++++++++++++++++++++++++++++++++++-----
 test/collection.js | 61 ++++++++++++++++++++++++++++++++++++--
 2 files changed, 124 insertions(+), 10 deletions(-)

diff --git a/backbone.js b/backbone.js
index cedcf04a3..fcd29d12f 100644
--- a/backbone.js
+++ b/backbone.js
@@ -828,16 +828,75 @@
       return this.models[index];
     },
 
+    // Perform a binary search for a model in a sorted collection.
+    search: function (toFind, options) {
+      if (!this.comparator) throw new Error('Cannot search an unsorted Collection');
+      options || (options = {});
+
+      // Create `compare` function for searching.
+      var compare;
+      if (_.isFunction(toFind)) {
+        // User provided the `compare` function.
+        compare = toFind;
+      } else if (_.isFunction(this.comparator)) {
+        // Use the comparator function, `toFind` is a model.
+        if (this.comparator.length === 2) {
+          compare = _(this.comparator).bind(this, toFind);
+        } else {
+          compare = _(function (valResult, model) {
+            var modelResult = this.comparator(model);
+            return valResult === modelResult ? 0 : (valResult > modelResult ? 1 : -1);
+          }).bind(this, this.comparator(toFind));
+        }
+      } else {
+        // Comparator is a string indicating the model property used to sort
+        // `toFind` is value sought.
+        compare = _(function (model) {
+          var modelValue = model.get(this.comparator);
+          return toFind === modelValue ? 0 : (toFind > modelValue ? 1 : -1);
+        }).bind(this);
+      }
+
+      // Perform binary search.
+      var found = false, max = this.length - 1, min = 0, index, relValue;
+      while (max >= min && !found) {
+        index = Math.floor((max + min) / 2);
+        relValue = compare(this.at(index));
+        if (relValue > 0) {
+          min = index + 1;
+        } else if (relValue < 0) {
+          max = index - 1;
+        } else if (options.getMax && index < max && compare(this.at(index + 1)) === 0) {
+          min = index + 1;
+        } else if (options.getMin && index > min && compare(this.at(index - 1)) === 0) {
+          max = index - 1;
+        } else {
+          found = true;
+        }
+      }
+      if (!found) return options.returnIndex ? -1 : void 0;
+      return options.returnIndex ? index : this.at(index);
+    },
+
     // Return models with matching attributes. Useful for simple cases of
     // `filter`.
     where: function(attrs, first) {
-      if (_.isEmpty(attrs)) return first ? void 0 : [];
-      return this[first ? 'find' : 'filter'](function(model) {
-        for (var key in attrs) {
-          if (attrs[key] !== model.get(key)) return false;
-        }
-        return true;
-      });
+      if (_.isEmpty(attrs)) {
+        return first ? void 0 : [];
+      } else if (!_.isEqual(_.keys(attrs), [this.comparator])) {
+        return this[first ? 'find' : 'filter'](function(model) {
+          for (var key in attrs) {
+            if (attrs[key] !== model.get(key)) return false;
+          }
+          return true;
+        });
+      } else if (first) {
+        return [this.search(attrs[this.comparator], {getMin: true})];
+      } else {
+        var minIndex = this.search(attrs[this.comparator], {returnIndex: true, getMin: true});
+        var maxIndex = this.search(attrs[this.comparator], {returnIndex: true, getMax: true});
+        return !minIndex ? [] : this.models.slice(minIndex, maxIndex + 1);
+      }
     },
 
     // Return the first model with matching attributes. Useful for simple cases
diff --git a/test/collection.js b/test/collection.js
index 8f518143d..be5ebe8b2 100644
--- a/test/collection.js
+++ b/test/collection.js
@@ -547,15 +547,70 @@
     equal(JSON.stringify(col), '[{"id":3,"label":"a"},{"id":2,"label":"b"},{"id":1,"label":"c"},{"id":0,"label":"d"}]');
   });
 
-  test("where and findWhere", 8, function() {
+  test("search", 12, function() {
+    var model1 = new Backbone.Model({a: 0});
+    var model2 = new Backbone.Model({a: 3});
+    var models = [
+      model1, {a: 1}, {a: 1}, {a: 1}, {a: 2}, model2
+    ];
+    var coll = new Backbone.Collection(models, {
+      comparator: 'a'
+    });
+    
+    equal(coll.search(1).get('a'), 1);
+    equal(coll.search(1, {getMin: true}), coll.at(1));
+    equal(coll.search(1, {getMax: true}), coll.at(3));
+    equal(coll.search(2, {returnIndex: true}), 4);
+    equal(coll.search(3, {returnIndex: true}), 5);
+    equal(coll.search(4, {returnIndex: true}), -1);
+    ok(!coll.search(4));
+
+    equal(coll.search(function (model) {
+      var v = model.get('a');
+      if (v < 2) return 1;
+      if (v > 2) return -1;
+      return 0;
+    }).get('a'), 2);
+
+    var col2 = new Backbone.Collection(models, {
+      comparator: function (m) {
+        return 5 - m.get('a');
+      }
+    });
+    equal(col2.search(model1, {returnIndex: true}), 5);
+    equal(col2.search(model2, {returnIndex: true}), 0);
+
+    var col3 = new Backbone.Collection(models, {
+      comparator: function (m1, m2) {
+        return m2.get('a') - m1.get('a');
+      }
+    });
+    equal(col3.search(model1), model1);
+    equal(col3.search(model2), model2);
+  });
+
+  test("where and findWhere", 16, function() {
     var model = new Backbone.Model({a: 1});
-    var coll = new Backbone.Collection([
+    var models = [
       model,
       {a: 1},
       {a: 1, b: 2},
       {a: 2, b: 2},
       {a: 3}
-    ]);
+    ];
+    var coll = new Backbone.Collection(models);
+    equal(coll.where({a: 1}).length, 3);
+    equal(coll.where({a: 2}).length, 1);
+    equal(coll.where({a: 3}).length, 1);
+    equal(coll.where({b: 1}).length, 0);
+    equal(coll.where({b: 2}).length, 2);
+    equal(coll.where({a: 1, b: 2}).length, 1);
+    equal(coll.findWhere({a: 1}), model);
+    equal(coll.findWhere({a: 4}), void 0);
+
+    var col2 = new Backbone.Collection(models, {
+      comparator: 'a'
+    });
     equal(coll.where({a: 1}).length, 3);
     equal(coll.where({a: 2}).length, 1);
     equal(coll.where({a: 3}).length, 1);

From 39ffec8c6b8b2a6e8a5333be37e048d8364d11bf Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Wed, 25 Jun 2014 19:53:21 +0100
Subject: [PATCH 02/11] fixed binary search

Fixed small bugs with `where` and `findWhere` and the erroneous tests
which didn't catch these issues.
---
 backbone.js        |  4 ++--
 test/collection.js | 16 ++++++++--------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/backbone.js b/backbone.js
index fcd29d12f..991583037 100644
--- a/backbone.js
+++ b/backbone.js
@@ -891,11 +891,11 @@
           return true;
         });
       } else if (first) {
-        return [this.search(attrs[this.comparator], {getMin: true})];
+        return this.search(attrs[this.comparator], {getMin: true});
       } else {
         var minIndex = this.search(attrs[this.comparator], {returnIndex: true, getMin: true});
         var maxIndex = this.search(attrs[this.comparator], {returnIndex: true, getMax: true});
-        return !minIndex ? [] : this.models.slice(minIndex, maxIndex + 1);
+        return minIndex == null ? [] : this.models.slice(minIndex, maxIndex + 1);
       }
     },
 
diff --git a/test/collection.js b/test/collection.js
index be5ebe8b2..7cdabd333 100644
--- a/test/collection.js
+++ b/test/collection.js
@@ -611,14 +611,14 @@
     var col2 = new Backbone.Collection(models, {
       comparator: 'a'
     });
-    equal(coll.where({a: 1}).length, 3);
-    equal(coll.where({a: 2}).length, 1);
-    equal(coll.where({a: 3}).length, 1);
-    equal(coll.where({b: 1}).length, 0);
-    equal(coll.where({b: 2}).length, 2);
-    equal(coll.where({a: 1, b: 2}).length, 1);
-    equal(coll.findWhere({a: 1}), model);
-    equal(coll.findWhere({a: 4}), void 0);
+    equal(col2.where({a: 1}).length, 3);
+    equal(col2.where({a: 2}).length, 1);
+    equal(col2.where({a: 3}).length, 1);
+    equal(col2.where({b: 1}).length, 0);
+    equal(col2.where({b: 2}).length, 2);
+    equal(col2.where({a: 1, b: 2}).length, 1);
+    equal(col2.findWhere({a: 1}), model);
+    equal(col2.findWhere({a: 4}), void 0);
   });
 
   test("Underscore methods", 16, function() {

From bdbc9bd9e1bcebf430fe2d301a9d9fa6dca351ef Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Thu, 26 Jun 2014 01:25:44 +0100
Subject: [PATCH 03/11] alter code to better fit previous style

---
 backbone.js | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/backbone.js b/backbone.js
index 991583037..361d25a93 100644
--- a/backbone.js
+++ b/backbone.js
@@ -836,25 +836,25 @@
       // Create `compare` function for searching.
       var compare;
       if (_.isFunction(toFind)) {
-        // User provided the `compare` function.
+        // The user has provided the `compare` function.
         compare = toFind;
       } else if (_.isFunction(this.comparator)) {
         // Use the comparator function, `toFind` is a model.
         if (this.comparator.length === 2) {
-          compare = _(this.comparator).bind(this, toFind);
+          compare = _.bind(this.comparator, this, toFind);
         } else {
-          compare = _(function (valResult, model) {
+          compare = _.bind(function (valResult, model) {
             var modelResult = this.comparator(model);
             return valResult === modelResult ? 0 : (valResult > modelResult ? 1 : -1);
-          }).bind(this, this.comparator(toFind));
+          }, this, this.comparator(toFind));
         }
       } else {
-        // Comparator is a string indicating the model property used to sort
-        // `toFind` is value sought.
-        compare = _(function (model) {
+        // `comparator` is a string indicating the model property used to sort
+        // `toFind` is the value sought.
+        compare = _.bind(function (model) {
           var modelValue = model.get(this.comparator);
           return toFind === modelValue ? 0 : (toFind > modelValue ? 1 : -1);
-        }).bind(this);
+        }, this);
       }
 
       // Perform binary search.

From c64e5d84013258c73e4db437aa9ffdcec06c3d73 Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Thu, 26 Jun 2014 01:31:04 +0100
Subject: [PATCH 04/11] add style comment backticks

---
 backbone.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/backbone.js b/backbone.js
index 361d25a93..46b5e7a33 100644
--- a/backbone.js
+++ b/backbone.js
@@ -839,7 +839,7 @@
         // The user has provided the `compare` function.
         compare = toFind;
       } else if (_.isFunction(this.comparator)) {
-        // Use the comparator function, `toFind` is a model.
+        // Use the `comparator` function, `toFind` is a model.
         if (this.comparator.length === 2) {
           compare = _.bind(this.comparator, this, toFind);
         } else {

From 8a04f02ce23246eaa8a99eebcfc794592b351579 Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Thu, 21 Aug 2014 21:38:56 +0100
Subject: [PATCH 05/11] bind `toFind` and only return index

If `toFind` is a function, the `compare` method will be bound to the
model.

Removed option to return model and always return index.
---
 backbone.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/backbone.js b/backbone.js
index 46b5e7a33..a678a25db 100644
--- a/backbone.js
+++ b/backbone.js
@@ -837,7 +837,7 @@
       var compare;
       if (_.isFunction(toFind)) {
         // The user has provided the `compare` function.
-        compare = toFind;
+        compare = _.bind(toFind, this);
       } else if (_.isFunction(this.comparator)) {
         // Use the `comparator` function, `toFind` is a model.
         if (this.comparator.length === 2) {
@@ -874,8 +874,8 @@
           found = true;
         }
       }
-      if (!found) return options.returnIndex ? -1 : void 0;
-      return options.returnIndex ? index : this.at(index);
+      
+      return found ? index : -1;
     },
 
     // Return models with matching attributes. Useful for simple cases of

From 2c17b4e44fdfff7bdfdeef3711ecebeb7390d24e Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Thu, 21 Aug 2014 21:59:14 +0100
Subject: [PATCH 06/11] fixed bugs and tests from last commit

---
 backbone.js        |  6 +++---
 test/collection.js | 25 ++++++++++---------------
 2 files changed, 13 insertions(+), 18 deletions(-)

diff --git a/backbone.js b/backbone.js
index a678a25db..ae146cfb6 100644
--- a/backbone.js
+++ b/backbone.js
@@ -891,10 +891,10 @@
           return true;
         });
       } else if (first) {
-        return this.search(attrs[this.comparator], {getMin: true});
+        return this.at(this.search(attrs[this.comparator], {getMin: true}));
       } else {
-        var minIndex = this.search(attrs[this.comparator], {returnIndex: true, getMin: true});
-        var maxIndex = this.search(attrs[this.comparator], {returnIndex: true, getMax: true});
+        var minIndex = this.search(attrs[this.comparator], {getMin: true});
+        var maxIndex = this.search(attrs[this.comparator], {getMax: true});
         return minIndex == null ? [] : this.models.slice(minIndex, maxIndex + 1);
       }
     },
diff --git a/test/collection.js b/test/collection.js
index 7cdabd333..42fc31638 100644
--- a/test/collection.js
+++ b/test/collection.js
@@ -547,7 +547,7 @@
     equal(JSON.stringify(col), '[{"id":3,"label":"a"},{"id":2,"label":"b"},{"id":1,"label":"c"},{"id":0,"label":"d"}]');
   });
 
-  test("search", 12, function() {
+  test("search", 7, function() {
     var model1 = new Backbone.Model({a: 0});
     var model2 = new Backbone.Model({a: 3});
     var models = [
@@ -557,36 +557,31 @@
       comparator: 'a'
     });
     
-    equal(coll.search(1).get('a'), 1);
-    equal(coll.search(1, {getMin: true}), coll.at(1));
-    equal(coll.search(1, {getMax: true}), coll.at(3));
-    equal(coll.search(2, {returnIndex: true}), 4);
-    equal(coll.search(3, {returnIndex: true}), 5);
-    equal(coll.search(4, {returnIndex: true}), -1);
-    ok(!coll.search(4));
-
-    equal(coll.search(function (model) {
+    equal(coll.at(coll.search(1)).get('a'), 1);
+    equal(coll.search(1, {getMin: true}), 1);
+    equal(coll.search(1, {getMax: true}), 3);
+    ok(coll.search(4) === -1);
+
+    equal(coll.at(coll.search(function (model) {
       var v = model.get('a');
       if (v < 2) return 1;
       if (v > 2) return -1;
       return 0;
-    }).get('a'), 2);
+    })).get('a'), 2);
 
     var col2 = new Backbone.Collection(models, {
       comparator: function (m) {
         return 5 - m.get('a');
       }
     });
-    equal(col2.search(model1, {returnIndex: true}), 5);
-    equal(col2.search(model2, {returnIndex: true}), 0);
 
     var col3 = new Backbone.Collection(models, {
       comparator: function (m1, m2) {
         return m2.get('a') - m1.get('a');
       }
     });
-    equal(col3.search(model1), model1);
-    equal(col3.search(model2), model2);
+    equal(col3.at(col3.search(model1)), model1);
+    equal(col3.at(col3.search(model2)), model2);
   });
 
   test("where and findWhere", 16, function() {

From 667d3804850c276fe8d48be0283e033c1e31ccff Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Sat, 30 Aug 2014 17:56:02 +0100
Subject: [PATCH 07/11] prevent setting both `getMin` and `getMax`

---
 backbone.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/backbone.js b/backbone.js
index ae146cfb6..6f4464bb9 100644
--- a/backbone.js
+++ b/backbone.js
@@ -830,9 +830,11 @@
 
     // Perform a binary search for a model in a sorted collection.
     search: function (toFind, options) {
-      if (!this.comparator) throw new Error('Cannot search an unsorted Collection');
       options || (options = {});
 
+      if (!this.comparator) throw new Error('Cannot search an unsorted Collection');
+      if (options.getMin && options.getMax) throw new Error('Cannot set both getMin and getMax');
+
       // Create `compare` function for searching.
       var compare;
       if (_.isFunction(toFind)) {

From be8e07cbf6750eee3fe2aadc0d486f8f52dfdfe9 Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Sat, 3 Jan 2015 20:58:54 +0000
Subject: [PATCH 08/11] test _ to 1.7.0, use _.comparator, getMax bool

now only have `getMax` boolean, if this is not truthy then the min is
fetched
bump test underscore to 1.7.0 (unreleased)
---
 backbone.js               |   21 +-
 test/collection.js        |    4 +-
 test/vendor/underscore.js | 1208 +++++++++++++++++++++----------------
 3 files changed, 710 insertions(+), 523 deletions(-)

diff --git a/backbone.js b/backbone.js
index 6f4464bb9..703307417 100644
--- a/backbone.js
+++ b/backbone.js
@@ -829,11 +829,8 @@
     },
 
     // Perform a binary search for a model in a sorted collection.
-    search: function (toFind, options) {
-      options || (options = {});
-
+    search: function (toFind, getMax) {
       if (!this.comparator) throw new Error('Cannot search an unsorted Collection');
-      if (options.getMin && options.getMax) throw new Error('Cannot set both getMin and getMax');
 
       // Create `compare` function for searching.
       var compare;
@@ -846,16 +843,14 @@
           compare = _.bind(this.comparator, this, toFind);
         } else {
           compare = _.bind(function (valResult, model) {
-            var modelResult = this.comparator(model);
-            return valResult === modelResult ? 0 : (valResult > modelResult ? 1 : -1);
+            return _.comparator(valResult, this.comparator(model));
           }, this, this.comparator(toFind));
         }
       } else {
         // `comparator` is a string indicating the model property used to sort
         // `toFind` is the value sought.
         compare = _.bind(function (model) {
-          var modelValue = model.get(this.comparator);
-          return toFind === modelValue ? 0 : (toFind > modelValue ? 1 : -1);
+          return _.comparator(toFind, model.get(this.comparator));
         }, this);
       }
 
@@ -868,9 +863,9 @@
           min = index + 1;
         } else if (relValue < 0) {
           max = index - 1;
-        } else if (options.getMax && index < max && compare(this.at(index + 1)) === 0) {
+        } else if (getMax && index < max && compare(this.at(index + 1)) === 0) {
           min = index + 1;
-        } else if (options.getMin && index > min && compare(this.at(index - 1)) === 0) {
+        } else if (!getMax && index > min && compare(this.at(index - 1)) === 0) {
           max = index - 1;
         } else {
           found = true;
@@ -893,10 +888,10 @@
           return true;
         });
       } else if (first) {
-        return this.at(this.search(attrs[this.comparator], {getMin: true}));
+        return this.at(this.search(attrs[this.comparator]));
       } else {
-        var minIndex = this.search(attrs[this.comparator], {getMin: true});
-        var maxIndex = this.search(attrs[this.comparator], {getMax: true});
+        var minIndex = this.search(attrs[this.comparator]);
+        var maxIndex = this.search(attrs[this.comparator], true);
         return minIndex == null ? [] : this.models.slice(minIndex, maxIndex + 1);
       }
     },
diff --git a/test/collection.js b/test/collection.js
index 42fc31638..31395b95e 100644
--- a/test/collection.js
+++ b/test/collection.js
@@ -558,8 +558,8 @@
     });
     
     equal(coll.at(coll.search(1)).get('a'), 1);
-    equal(coll.search(1, {getMin: true}), 1);
-    equal(coll.search(1, {getMax: true}), 3);
+    equal(coll.search(1), 1);
+    equal(coll.search(1, true), 3);
     ok(coll.search(4) === -1);
 
     equal(coll.at(coll.search(function (model) {
diff --git a/test/vendor/underscore.js b/test/vendor/underscore.js
index 9a4cabecf..62bcf9006 100644
--- a/test/vendor/underscore.js
+++ b/test/vendor/underscore.js
@@ -1,4 +1,4 @@
-//     Underscore.js 1.6.0
+//     Underscore.js 1.7.0
 //     http://underscorejs.org
 //     (c) 2009-2014 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 //     Underscore may be freely distributed under the MIT license.
@@ -14,9 +14,6 @@
   // Save the previous value of the `_` variable.
   var previousUnderscore = root._;
 
-  // Establish the object that gets returned to break out of a loop iteration.
-  var breaker = {};
-
   // Save bytes in the minified (but not gzipped) version:
   var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
 
@@ -24,25 +21,19 @@
   var
     push             = ArrayProto.push,
     slice            = ArrayProto.slice,
-    concat           = ArrayProto.concat,
     toString         = ObjProto.toString,
     hasOwnProperty   = ObjProto.hasOwnProperty;
 
   // All **ECMAScript 5** native function implementations that we hope to use
   // are declared here.
   var
-    nativeForEach      = ArrayProto.forEach,
-    nativeMap          = ArrayProto.map,
-    nativeReduce       = ArrayProto.reduce,
-    nativeReduceRight  = ArrayProto.reduceRight,
-    nativeFilter       = ArrayProto.filter,
-    nativeEvery        = ArrayProto.every,
-    nativeSome         = ArrayProto.some,
-    nativeIndexOf      = ArrayProto.indexOf,
-    nativeLastIndexOf  = ArrayProto.lastIndexOf,
     nativeIsArray      = Array.isArray,
     nativeKeys         = Object.keys,
-    nativeBind         = FuncProto.bind;
+    nativeBind         = FuncProto.bind,
+    nativeCreate       = Object.create;
+
+  // Reusable constructor function for prototype setting.
+  var Ctor = function(){};
 
   // Create a safe reference to the Underscore object for use below.
   var _ = function(obj) {
@@ -53,8 +44,7 @@
 
   // Export the Underscore object for **Node.js**, with
   // backwards-compatibility for the old `require()` API. If we're in
-  // the browser, add `_` as a global object via a string identifier,
-  // for Closure Compiler "advanced" mode.
+  // the browser, add `_` as a global object.
   if (typeof exports !== 'undefined') {
     if (typeof module !== 'undefined' && module.exports) {
       exports = module.exports = _;
@@ -65,161 +55,235 @@
   }
 
   // Current version.
-  _.VERSION = '1.6.0';
+  _.VERSION = '1.7.0';
+
+  // Internal function that returns an efficient (for current engines) version
+  // of the passed-in callback, to be repeatedly applied in other Underscore
+  // functions.
+  var optimizeCb = function(func, context, argCount) {
+    if (context === void 0) return func;
+    switch (argCount == null ? 3 : argCount) {
+      case 1: return function(value) {
+        return func.call(context, value);
+      };
+      case 2: return function(value, other) {
+        return func.call(context, value, other);
+      };
+      case 3: return function(value, index, collection) {
+        return func.call(context, value, index, collection);
+      };
+      case 4: return function(accumulator, value, index, collection) {
+        return func.call(context, accumulator, value, index, collection);
+      };
+    }
+    return function() {
+      return func.apply(context, arguments);
+    };
+  };
+
+  // A mostly-internal function to generate callbacks that can be applied
+  // to each element in a collection, returning the desired result — either
+  // identity, an arbitrary callback, a property matcher, or a property accessor.
+  var cb = function(value, context, argCount) {
+    if (value == null) return _.identity;
+    if (_.isFunction(value)) return optimizeCb(value, context, argCount);
+    if (_.isObject(value)) return _.matches(value);
+    return _.property(value);
+  };
+  _.iteratee = function(value, context) {
+    return cb(value, context, Infinity);
+  };
+
+  // An internal function for creating assigner functions.
+  var createAssigner = function(keysFunc) {
+    return function(obj) {
+      var length = arguments.length;
+      if (length < 2 || obj == null) return obj;
+      for (var index = 0; index < length; index++) {
+        var source = arguments[index],
+            keys = keysFunc(source),
+            l = keys.length;
+        for (var i = 0; i < l; i++) {
+          var key = keys[i];
+          obj[key] = source[key];
+        }
+      }
+      return obj;
+    };
+  };
+
+  // An internal function for creating a new object that inherits from another.
+  var baseCreate = function(prototype) {
+    if (!_.isObject(prototype)) return {};
+    if (nativeCreate) return nativeCreate(prototype);
+    Ctor.prototype = prototype;
+    var result = new Ctor;
+    Ctor.prototype = null;
+    return result;
+  };
 
   // Collection Functions
   // --------------------
 
   // The cornerstone, an `each` implementation, aka `forEach`.
-  // Handles objects with the built-in `forEach`, arrays, and raw objects.
-  // Delegates to **ECMAScript 5**'s native `forEach` if available.
-  var each = _.each = _.forEach = function(obj, iterator, context) {
+  // Handles raw objects in addition to array-likes. Treats all
+  // sparse array-likes as if they were dense.
+  _.each = _.forEach = function(obj, iteratee, context) {
     if (obj == null) return obj;
-    if (nativeForEach && obj.forEach === nativeForEach) {
-      obj.forEach(iterator, context);
-    } else if (obj.length === +obj.length) {
-      for (var i = 0, length = obj.length; i < length; i++) {
-        if (iterator.call(context, obj[i], i, obj) === breaker) return;
+    iteratee = optimizeCb(iteratee, context);
+    var i, length = obj.length;
+    if (length === +length) {
+      for (i = 0; i < length; i++) {
+        iteratee(obj[i], i, obj);
       }
     } else {
       var keys = _.keys(obj);
-      for (var i = 0, length = keys.length; i < length; i++) {
-        if (iterator.call(context, obj[keys[i]], keys[i], obj) === breaker) return;
+      for (i = 0, length = keys.length; i < length; i++) {
+        iteratee(obj[keys[i]], keys[i], obj);
       }
     }
     return obj;
   };
 
-  // Return the results of applying the iterator to each element.
-  // Delegates to **ECMAScript 5**'s native `map` if available.
-  _.map = _.collect = function(obj, iterator, context) {
-    var results = [];
-    if (obj == null) return results;
-    if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
-    each(obj, function(value, index, list) {
-      results.push(iterator.call(context, value, index, list));
-    });
+  // Return the results of applying the iteratee to each element.
+  _.map = _.collect = function(obj, iteratee, context) {
+    if (obj == null) return [];
+    iteratee = cb(iteratee, context);
+    var keys = obj.length !== +obj.length && _.keys(obj),
+        length = (keys || obj).length,
+        results = Array(length),
+        currentKey;
+    for (var index = 0; index < length; index++) {
+      currentKey = keys ? keys[index] : index;
+      results[index] = iteratee(obj[currentKey], currentKey, obj);
+    }
     return results;
   };
 
-  var reduceError = 'Reduce of empty array with no initial value';
-
   // **Reduce** builds up a single result from a list of values, aka `inject`,
-  // or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
-  _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
-    var initial = arguments.length > 2;
+  // or `foldl`.
+  _.reduce = _.foldl = _.inject = function(obj, iteratee, memo, context) {
     if (obj == null) obj = [];
-    if (nativeReduce && obj.reduce === nativeReduce) {
-      if (context) iterator = _.bind(iterator, context);
-      return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
+    iteratee = optimizeCb(iteratee, context, 4);
+    var keys = obj.length !== +obj.length && _.keys(obj),
+        length = (keys || obj).length,
+        index = 0, currentKey;
+    if (arguments.length < 3) {
+      memo = obj[keys ? keys[index++] : index++];
+    }
+    for (; index < length; index++) {
+      currentKey = keys ? keys[index] : index;
+      memo = iteratee(memo, obj[currentKey], currentKey, obj);
     }
-    each(obj, function(value, index, list) {
-      if (!initial) {
-        memo = value;
-        initial = true;
-      } else {
-        memo = iterator.call(context, memo, value, index, list);
-      }
-    });
-    if (!initial) throw new TypeError(reduceError);
     return memo;
   };
 
   // The right-associative version of reduce, also known as `foldr`.
-  // Delegates to **ECMAScript 5**'s native `reduceRight` if available.
-  _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
-    var initial = arguments.length > 2;
+  _.reduceRight = _.foldr = function(obj, iteratee, memo, context) {
     if (obj == null) obj = [];
-    if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
-      if (context) iterator = _.bind(iterator, context);
-      return initial ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
+    iteratee = optimizeCb(iteratee, context, 4);
+    var keys = obj.length !== + obj.length && _.keys(obj),
+        index = (keys || obj).length,
+        currentKey;
+    if (arguments.length < 3) {
+      memo = obj[keys ? keys[--index] : --index];
     }
-    var length = obj.length;
-    if (length !== +length) {
-      var keys = _.keys(obj);
-      length = keys.length;
+    while (index-- > 0) {
+      currentKey = keys ? keys[index] : index;
+      memo = iteratee(memo, obj[currentKey], currentKey, obj);
     }
-    each(obj, function(value, index, list) {
-      index = keys ? keys[--length] : --length;
-      if (!initial) {
-        memo = obj[index];
-        initial = true;
+    return memo;
+  };
+
+  // **Transform** is an alternative to reduce that transforms `obj` to a new
+  // `accumulator` object.
+  _.transform = function(obj, iteratee, accumulator, context) {
+    if (accumulator == null) {
+      if (_.isArray(obj)) {
+        accumulator = [];
+      } else if (_.isObject(obj)) {
+        var Ctor = obj.constructor;
+        accumulator = baseCreate(typeof Ctor == 'function' && Ctor.prototype);
       } else {
-        memo = iterator.call(context, memo, obj[index], index, list);
+        accumulator = {};
       }
-    });
-    if (!initial) throw new TypeError(reduceError);
-    return memo;
+    }
+    if (obj == null) return accumulator;
+    iteratee = optimizeCb(iteratee, context, 4);
+    var keys = obj.length !== +obj.length && _.keys(obj),
+      length = (keys || obj).length,
+      index, currentKey;
+    for (index = 0; index < length; index++) {
+      currentKey = keys ? keys[index] : index;
+      if (iteratee(accumulator, obj[currentKey], currentKey, obj) === false) break;
+    }
+    return accumulator;
   };
 
   // Return the first value which passes a truth test. Aliased as `detect`.
   _.find = _.detect = function(obj, predicate, context) {
-    var result;
-    any(obj, function(value, index, list) {
-      if (predicate.call(context, value, index, list)) {
-        result = value;
-        return true;
-      }
-    });
-    return result;
+    var key;
+    if (obj.length === +obj.length) {
+      key = _.findIndex(obj, predicate, context);
+    } else {
+      key = _.findKey(obj, predicate, context);
+    }
+    if (key !== void 0 && key !== -1) return obj[key];
   };
 
   // Return all the elements that pass a truth test.
-  // Delegates to **ECMAScript 5**'s native `filter` if available.
   // Aliased as `select`.
   _.filter = _.select = function(obj, predicate, context) {
     var results = [];
     if (obj == null) return results;
-    if (nativeFilter && obj.filter === nativeFilter) return obj.filter(predicate, context);
-    each(obj, function(value, index, list) {
-      if (predicate.call(context, value, index, list)) results.push(value);
+    predicate = cb(predicate, context);
+    _.each(obj, function(value, index, list) {
+      if (predicate(value, index, list)) results.push(value);
     });
     return results;
   };
 
   // Return all the elements for which a truth test fails.
   _.reject = function(obj, predicate, context) {
-    return _.filter(obj, function(value, index, list) {
-      return !predicate.call(context, value, index, list);
-    }, context);
+    return _.filter(obj, _.negate(cb(predicate)), context);
   };
 
   // Determine whether all of the elements match a truth test.
-  // Delegates to **ECMAScript 5**'s native `every` if available.
   // Aliased as `all`.
   _.every = _.all = function(obj, predicate, context) {
-    predicate || (predicate = _.identity);
-    var result = true;
-    if (obj == null) return result;
-    if (nativeEvery && obj.every === nativeEvery) return obj.every(predicate, context);
-    each(obj, function(value, index, list) {
-      if (!(result = result && predicate.call(context, value, index, list))) return breaker;
-    });
-    return !!result;
+    if (obj == null) return true;
+    predicate = cb(predicate, context);
+    var keys = obj.length !== +obj.length && _.keys(obj),
+        length = (keys || obj).length,
+        index, currentKey;
+    for (index = 0; index < length; index++) {
+      currentKey = keys ? keys[index] : index;
+      if (!predicate(obj[currentKey], currentKey, obj)) return false;
+    }
+    return true;
   };
 
   // Determine if at least one element in the object matches a truth test.
-  // Delegates to **ECMAScript 5**'s native `some` if available.
   // Aliased as `any`.
-  var any = _.some = _.any = function(obj, predicate, context) {
-    predicate || (predicate = _.identity);
-    var result = false;
-    if (obj == null) return result;
-    if (nativeSome && obj.some === nativeSome) return obj.some(predicate, context);
-    each(obj, function(value, index, list) {
-      if (result || (result = predicate.call(context, value, index, list))) return breaker;
-    });
-    return !!result;
+  _.some = _.any = function(obj, predicate, context) {
+    if (obj == null) return false;
+    predicate = cb(predicate, context);
+    var keys = obj.length !== +obj.length && _.keys(obj),
+        length = (keys || obj).length,
+        index, currentKey;
+    for (index = 0; index < length; index++) {
+      currentKey = keys ? keys[index] : index;
+      if (predicate(obj[currentKey], currentKey, obj)) return true;
+    }
+    return false;
   };
 
   // Determine if the array or object contains a given value (using `===`).
-  // Aliased as `include`.
-  _.contains = _.include = function(obj, target) {
+  // Aliased as `includes` and `include`.
+  _.contains = _.includes = _.include = function(obj, target, fromIndex) {
     if (obj == null) return false;
-    if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
-    return any(obj, function(value) {
-      return value === target;
-    });
+    if (obj.length !== +obj.length) obj = _.values(obj);
+    return _.indexOf(obj, target, typeof fromIndex == 'number' && fromIndex) >= 0;
   };
 
   // Invoke a method (with arguments) on every item in a collection.
@@ -248,51 +312,67 @@
     return _.find(obj, _.matches(attrs));
   };
 
-  // Return the maximum element or (element-based computation).
-  // Can't optimize arrays of integers longer than 65,535 elements.
-  // See [WebKit Bug 80797](https://bugs.webkit.org/show_bug.cgi?id=80797)
-  _.max = function(obj, iterator, context) {
-    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
-      return Math.max.apply(Math, obj);
-    }
-    var result = -Infinity, lastComputed = -Infinity;
-    each(obj, function(value, index, list) {
-      var computed = iterator ? iterator.call(context, value, index, list) : value;
-      if (computed > lastComputed) {
-        result = value;
-        lastComputed = computed;
+  // Return the maximum element (or element-based computation).
+  _.max = function(obj, iteratee, context) {
+    var result = -Infinity, lastComputed = -Infinity,
+        value, computed;
+    if (iteratee == null && obj != null) {
+      obj = obj.length === +obj.length ? obj : _.values(obj);
+      for (var i = 0, length = obj.length; i < length; i++) {
+        value = obj[i];
+        if (value > result) {
+          result = value;
+        }
       }
-    });
+    } else {
+      iteratee = cb(iteratee, context);
+      _.each(obj, function(value, index, list) {
+        computed = iteratee(value, index, list);
+        if (computed > lastComputed || computed === -Infinity && result === -Infinity) {
+          result = value;
+          lastComputed = computed;
+        }
+      });
+    }
     return result;
   };
 
   // Return the minimum element (or element-based computation).
-  _.min = function(obj, iterator, context) {
-    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
-      return Math.min.apply(Math, obj);
-    }
-    var result = Infinity, lastComputed = Infinity;
-    each(obj, function(value, index, list) {
-      var computed = iterator ? iterator.call(context, value, index, list) : value;
-      if (computed < lastComputed) {
-        result = value;
-        lastComputed = computed;
+  _.min = function(obj, iteratee, context) {
+    var result = Infinity, lastComputed = Infinity,
+        value, computed;
+    if (iteratee == null && obj != null) {
+      obj = obj.length === +obj.length ? obj : _.values(obj);
+      for (var i = 0, length = obj.length; i < length; i++) {
+        value = obj[i];
+        if (value < result) {
+          result = value;
+        }
       }
-    });
+    } else {
+      iteratee = cb(iteratee, context);
+      _.each(obj, function(value, index, list) {
+        computed = iteratee(value, index, list);
+        if (computed < lastComputed || computed === Infinity && result === Infinity) {
+          result = value;
+          lastComputed = computed;
+        }
+      });
+    }
     return result;
   };
 
-  // Shuffle an array, using the modern version of the
+  // Shuffle a collection, using the modern version of the
   // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
   _.shuffle = function(obj) {
-    var rand;
-    var index = 0;
-    var shuffled = [];
-    each(obj, function(value) {
-      rand = _.random(index++);
-      shuffled[index - 1] = shuffled[rand];
-      shuffled[rand] = value;
-    });
+    var set = obj && obj.length === +obj.length ? obj : _.values(obj);
+    var length = set.length;
+    var shuffled = Array(length);
+    for (var index = 0, rand; index < length; index++) {
+      rand = _.random(0, index);
+      if (rand !== index) shuffled[index] = shuffled[rand];
+      shuffled[rand] = set[index];
+    }
     return shuffled;
   };
 
@@ -307,41 +387,28 @@
     return _.shuffle(obj).slice(0, Math.max(0, n));
   };
 
-  // An internal function to generate lookup iterators.
-  var lookupIterator = function(value) {
-    if (value == null) return _.identity;
-    if (_.isFunction(value)) return value;
-    return _.property(value);
-  };
-
-  // Sort the object's values by a criterion produced by an iterator.
-  _.sortBy = function(obj, iterator, context) {
-    iterator = lookupIterator(iterator);
+  // Sort the object's values by a criterion produced by an iteratee.
+  _.sortBy = function(obj, iteratee, context) {
+    iteratee = cb(iteratee, context);
     return _.pluck(_.map(obj, function(value, index, list) {
       return {
         value: value,
         index: index,
-        criteria: iterator.call(context, value, index, list)
+        criteria: iteratee(value, index, list)
       };
     }).sort(function(left, right) {
-      var a = left.criteria;
-      var b = right.criteria;
-      if (a !== b) {
-        if (a > b || a === void 0) return 1;
-        if (a < b || b === void 0) return -1;
-      }
-      return left.index - right.index;
+      return _.comparator(left.criteria, right.criteria) || left.index - right.index;
     }), 'value');
   };
 
   // An internal function used for aggregate "group by" operations.
   var group = function(behavior) {
-    return function(obj, iterator, context) {
+    return function(obj, iteratee, context) {
       var result = {};
-      iterator = lookupIterator(iterator);
-      each(obj, function(value, index) {
-        var key = iterator.call(context, value, index, obj);
-        behavior(result, key, value);
+      iteratee = cb(iteratee, context);
+      _.each(obj, function(value, index) {
+        var key = iteratee(value, index, obj);
+        behavior(result, value, key);
       });
       return result;
     };
@@ -349,36 +416,23 @@
 
   // Groups the object's values by a criterion. Pass either a string attribute
   // to group by, or a function that returns the criterion.
-  _.groupBy = group(function(result, key, value) {
-    _.has(result, key) ? result[key].push(value) : result[key] = [value];
+  _.groupBy = group(function(result, value, key) {
+    if (_.has(result, key)) result[key].push(value); else result[key] = [value];
   });
 
   // Indexes the object's values by a criterion, similar to `groupBy`, but for
   // when you know that your index values will be unique.
-  _.indexBy = group(function(result, key, value) {
+  _.indexBy = group(function(result, value, key) {
     result[key] = value;
   });
 
   // Counts instances of an object that group by a certain criterion. Pass
   // either a string attribute to count by, or a function that returns the
   // criterion.
-  _.countBy = group(function(result, key) {
-    _.has(result, key) ? result[key]++ : result[key] = 1;
+  _.countBy = group(function(result, value, key) {
+    if (_.has(result, key)) result[key]++; else result[key] = 1;
   });
 
-  // Use a comparator function to figure out the smallest index at which
-  // an object should be inserted so as to maintain order. Uses binary search.
-  _.sortedIndex = function(array, obj, iterator, context) {
-    iterator = lookupIterator(iterator);
-    var value = iterator.call(context, obj);
-    var low = 0, high = array.length;
-    while (low < high) {
-      var mid = (low + high) >>> 1;
-      iterator.call(context, array[mid]) < value ? low = mid + 1 : high = mid;
-    }
-    return low;
-  };
-
   // Safely create a real, live array from anything iterable.
   _.toArray = function(obj) {
     if (!obj) return [];
@@ -390,7 +444,18 @@
   // Return the number of elements in an object.
   _.size = function(obj) {
     if (obj == null) return 0;
-    return (obj.length === +obj.length) ? obj.length : _.keys(obj).length;
+    return obj.length === +obj.length ? obj.length : _.keys(obj).length;
+  };
+
+  // Split a collection into two arrays: one whose elements all satisfy the given
+  // predicate, and one whose elements all do not satisfy the predicate.
+  _.partition = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var pass = [], fail = [];
+    _.each(obj, function(value, key, obj) {
+      (predicate(value, key, obj) ? pass : fail).push(value);
+    });
+    return [pass, fail];
   };
 
   // Array Functions
@@ -401,9 +466,8 @@
   // allows it to work with `_.map`.
   _.first = _.head = _.take = function(array, n, guard) {
     if (array == null) return void 0;
-    if ((n == null) || guard) return array[0];
-    if (n < 0) return [];
-    return slice.call(array, 0, n);
+    if (n == null || guard) return array[0];
+    return _.initial(array, array.length - n);
   };
 
   // Returns everything but the last entry of the array. Especially useful on
@@ -411,15 +475,15 @@
   // the array, excluding the last N. The **guard** check allows it to work with
   // `_.map`.
   _.initial = function(array, n, guard) {
-    return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
+    return slice.call(array, 0, Math.max(0, array.length - (n == null || guard ? 1 : n)));
   };
 
   // Get the last element of an array. Passing **n** will return the last N
   // values in the array. The **guard** check allows it to work with `_.map`.
   _.last = function(array, n, guard) {
     if (array == null) return void 0;
-    if ((n == null) || guard) return array[array.length - 1];
-    return slice.call(array, Math.max(array.length - n, 0));
+    if (n == null || guard) return array[array.length - 1];
+    return _.rest(array, Math.max(0, array.length - n));
   };
 
   // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
@@ -427,7 +491,7 @@
   // the rest N values in the array. The **guard**
   // check allows it to work with `_.map`.
   _.rest = _.tail = _.drop = function(array, n, guard) {
-    return slice.call(array, (n == null) || guard ? 1 : n);
+    return slice.call(array, n == null || guard ? 1 : n);
   };
 
   // Trim out all falsy values from an array.
@@ -436,23 +500,28 @@
   };
 
   // Internal implementation of a recursive `flatten` function.
-  var flatten = function(input, shallow, output) {
-    if (shallow && _.every(input, _.isArray)) {
-      return concat.apply(output, input);
-    }
-    each(input, function(value) {
-      if (_.isArray(value) || _.isArguments(value)) {
-        shallow ? push.apply(output, value) : flatten(value, shallow, output);
-      } else {
-        output.push(value);
+  var flatten = function(input, shallow, strict, startIndex) {
+    var output = [], idx = 0, value;
+    for (var i = startIndex || 0, length = input && input.length; i < length; i++) {
+      value = input[i];
+      if (value && value.length >= 0 && (_.isArray(value) || _.isArguments(value))) {
+        //flatten current level of array or arguments object
+        if (!shallow) value = flatten(value, shallow, strict);
+        var j = 0, len = value.length;
+        output.length += len;
+        while (j < len) {
+          output[idx++] = value[j++];
+        }
+      } else if (!strict) {
+        output[idx++] = value;
       }
-    });
+    }
     return output;
   };
 
   // Flatten out an array, either recursively (by default), or just one level.
   _.flatten = function(array, shallow) {
-    return flatten(array, shallow, []);
+    return flatten(array, shallow, false);
   };
 
   // Return a version of the array that does not contain the specified value(s).
@@ -460,72 +529,87 @@
     return _.difference(array, slice.call(arguments, 1));
   };
 
-  // Split an array into two arrays: one whose elements all satisfy the given
-  // predicate, and one whose elements all do not satisfy the predicate.
-  _.partition = function(array, predicate) {
-    var pass = [], fail = [];
-    each(array, function(elem) {
-      (predicate(elem) ? pass : fail).push(elem);
-    });
-    return [pass, fail];
-  };
-
   // Produce a duplicate-free version of the array. If the array has already
   // been sorted, you have the option of using a faster algorithm.
   // Aliased as `unique`.
-  _.uniq = _.unique = function(array, isSorted, iterator, context) {
-    if (_.isFunction(isSorted)) {
-      context = iterator;
-      iterator = isSorted;
+  _.uniq = _.unique = function(array, isSorted, iteratee, context) {
+    if (array == null) return [];
+    if (!_.isBoolean(isSorted)) {
+      context = iteratee;
+      iteratee = isSorted;
       isSorted = false;
     }
-    var initial = iterator ? _.map(array, iterator, context) : array;
-    var results = [];
+    if (iteratee != null) iteratee = cb(iteratee, context);
+    var result = [];
     var seen = [];
-    each(initial, function(value, index) {
-      if (isSorted ? (!index || seen[seen.length - 1] !== value) : !_.contains(seen, value)) {
-        seen.push(value);
-        results.push(array[index]);
+    for (var i = 0, length = array.length; i < length; i++) {
+      var value = array[i],
+          computed = iteratee ? iteratee(value, i, array) : value;
+      if (isSorted) {
+        if (!i || seen !== computed) result.push(value);
+        seen = computed;
+      } else if (iteratee) {
+        if (!_.contains(seen, computed)) {
+          seen.push(computed);
+          result.push(value);
+        }
+      } else if (!_.contains(result, value)) {
+        result.push(value);
       }
-    });
-    return results;
+    }
+    return result;
   };
 
   // Produce an array that contains the union: each distinct element from all of
   // the passed-in arrays.
   _.union = function() {
-    return _.uniq(_.flatten(arguments, true));
+    return _.uniq(flatten(arguments, true, true));
   };
 
   // Produce an array that contains every item shared between all the
   // passed-in arrays.
   _.intersection = function(array) {
-    var rest = slice.call(arguments, 1);
-    return _.filter(_.uniq(array), function(item) {
-      return _.every(rest, function(other) {
-        return _.contains(other, item);
-      });
-    });
+    if (array == null) return [];
+    var result = [];
+    var argsLength = arguments.length;
+    for (var i = 0, length = array.length; i < length; i++) {
+      var item = array[i];
+      if (_.contains(result, item)) continue;
+      for (var j = 1; j < argsLength; j++) {
+        if (!_.contains(arguments[j], item)) break;
+      }
+      if (j === argsLength) result.push(item);
+    }
+    return result;
   };
 
   // Take the difference between one array and a number of other arrays.
   // Only the elements present in just the first array will remain.
   _.difference = function(array) {
-    var rest = concat.apply(ArrayProto, slice.call(arguments, 1));
-    return _.filter(array, function(value){ return !_.contains(rest, value); });
+    var rest = flatten(arguments, true, true, 1);
+    return _.filter(array, function(value){
+      return !_.contains(rest, value);
+    });
   };
 
   // Zip together multiple lists into a single array -- elements that share
   // an index go together.
-  _.zip = function() {
-    var length = _.max(_.pluck(arguments, 'length').concat(0));
-    var results = new Array(length);
-    for (var i = 0; i < length; i++) {
-      results[i] = _.pluck(arguments, '' + i);
+  _.zip = function(array) {
+    if (array == null) return [];
+    var length = _.max(arguments, 'length').length;
+    var results = Array(length);
+    while (length-- > 0) {
+      results[length] = _.pluck(arguments, length);
     }
     return results;
   };
 
+  // Complement of _.zip. Unzip accepts an array of arrays and groups
+  // each array's elements on shared indices
+  _.unzip = function(array) {
+    return _.zip.apply(null, array);
+  };
+
   // Converts lists into objects. Pass either a single array of `[key, value]`
   // pairs, or two parallel arrays of the same length -- one of keys, and one of
   // the corresponding values.
@@ -542,40 +626,54 @@
     return result;
   };
 
-  // If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
-  // we need this function. Return the position of the first occurrence of an
-  // item in an array, or -1 if the item is not included in the array.
-  // Delegates to **ECMAScript 5**'s native `indexOf` if available.
+  // Return the position of the first occurrence of an item in an array,
+  // or -1 if the item is not included in the array.
   // If the array is large and already in sort order, pass `true`
   // for **isSorted** to use binary search.
   _.indexOf = function(array, item, isSorted) {
-    if (array == null) return -1;
-    var i = 0, length = array.length;
-    if (isSorted) {
-      if (typeof isSorted == 'number') {
-        i = (isSorted < 0 ? Math.max(0, length + isSorted) : isSorted);
-      } else {
-        i = _.sortedIndex(array, item);
-        return array[i] === item ? i : -1;
-      }
+    var i = 0, length = array && array.length;
+    if (typeof isSorted == 'number') {
+      i = isSorted < 0 ? Math.max(0, length + isSorted) : isSorted;
+    } else if (isSorted && length) {
+      i = _.sortedIndex(array, item);
+      return array[i] === item ? i : -1;
     }
-    if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item, isSorted);
     for (; i < length; i++) if (array[i] === item) return i;
     return -1;
   };
 
-  // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
   _.lastIndexOf = function(array, item, from) {
-    if (array == null) return -1;
-    var hasIndex = from != null;
-    if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) {
-      return hasIndex ? array.lastIndexOf(item, from) : array.lastIndexOf(item);
+    var idx = array ? array.length : 0;
+    if (typeof from == 'number') {
+      idx = from < 0 ? idx + from + 1 : Math.min(idx, from + 1);
     }
-    var i = (hasIndex ? from : array.length);
-    while (i--) if (array[i] === item) return i;
+    while (--idx >= 0) if (array[idx] === item) return idx;
     return -1;
   };
 
+  // Returns the first index on an array-like that passes a predicate test
+  _.findIndex = function(array, predicate, context) {
+    predicate = cb(predicate, context);
+    var length = array != null ? array.length : 0;
+    for (var i = 0; i < length; i++) {
+      if (predicate(array[i], i, array)) return i;
+    }
+    return -1;
+  };
+
+  // Use a comparator function to figure out the smallest index at which
+  // an object should be inserted so as to maintain order. Uses binary search.
+  _.sortedIndex = function(array, obj, iteratee, context) {
+    iteratee = cb(iteratee, context, 1);
+    var value = iteratee(obj);
+    var low = 0, high = array.length;
+    while (low < high) {
+      var mid = Math.floor((low + high) / 2);
+      if (_.comparator(iteratee(array[mid]), value) < 0) low = mid + 1; else high = mid;
+    }
+    return low;
+  };
+
   // Generate an integer Array containing an arithmetic progression. A port of
   // the native Python `range()` function. See
   // [the Python documentation](http://docs.python.org/library/functions.html#range).
@@ -584,15 +682,13 @@
       stop = start || 0;
       start = 0;
     }
-    step = arguments[2] || 1;
+    step = step || 1;
 
     var length = Math.max(Math.ceil((stop - start) / step), 0);
-    var idx = 0;
-    var range = new Array(length);
+    var range = Array(length);
 
-    while(idx < length) {
-      range[idx++] = start;
-      start += step;
+    for (var idx = 0; idx < length; idx++, start += step) {
+      range[idx] = start;
     }
 
     return range;
@@ -601,25 +697,25 @@
   // Function (ahem) Functions
   // ------------------
 
-  // Reusable constructor function for prototype setting.
-  var ctor = function(){};
+  // Determines whether to execute a function as a constructor
+  // or a normal function with the provided arguments
+  var executeBound = function(sourceFunc, boundFunc, context, callingContext, args) {
+    if (!(callingContext instanceof boundFunc)) return sourceFunc.apply(context, args);
+    var self = baseCreate(sourceFunc.prototype);
+    var result = sourceFunc.apply(self, args);
+    if (_.isObject(result)) return result;
+    return self;
+  };
 
   // Create a function bound to a given object (assigning `this`, and arguments,
   // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
   // available.
   _.bind = function(func, context) {
-    var args, bound;
     if (nativeBind && func.bind === nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
-    if (!_.isFunction(func)) throw new TypeError;
-    args = slice.call(arguments, 2);
-    return bound = function() {
-      if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
-      ctor.prototype = func.prototype;
-      var self = new ctor;
-      ctor.prototype = null;
-      var result = func.apply(self, args.concat(slice.call(arguments)));
-      if (Object(result) === result) return result;
-      return self;
+    if (!_.isFunction(func)) throw new TypeError('Bind must be called on a function');
+    var args = slice.call(arguments, 2);
+    return function bound() {
+      return executeBound(func, bound, context, this, args.concat(slice.call(arguments)));
     };
   };
 
@@ -628,14 +724,14 @@
   // as a placeholder, allowing any combination of arguments to be pre-filled.
   _.partial = function(func) {
     var boundArgs = slice.call(arguments, 1);
-    return function() {
+    return function bound() {
       var position = 0;
       var args = boundArgs.slice();
       for (var i = 0, length = args.length; i < length; i++) {
         if (args[i] === _) args[i] = arguments[position++];
       }
       while (position < arguments.length) args.push(arguments[position++]);
-      return func.apply(this, args);
+      return executeBound(func, bound, this, this, args);
     };
   };
 
@@ -643,34 +739,39 @@
   // are the method names to be bound. Useful for ensuring that all callbacks
   // defined on an object belong to it.
   _.bindAll = function(obj) {
-    var funcs = slice.call(arguments, 1);
-    if (funcs.length === 0) throw new Error('bindAll must be passed function names');
-    each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
+    var i, length = arguments.length, key;
+    if (length <= 1) throw new Error('bindAll must be passed function names');
+    for (i = 1; i < length; i++) {
+      key = arguments[i];
+      obj[key] = _.bind(obj[key], obj);
+    }
     return obj;
   };
 
   // Memoize an expensive function by storing its results.
   _.memoize = function(func, hasher) {
-    var memo = {};
-    hasher || (hasher = _.identity);
-    return function() {
-      var key = hasher.apply(this, arguments);
-      return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
+    var memoize = function(key) {
+      var cache = memoize.cache;
+      var address = '' + (hasher ? hasher.apply(this, arguments) : key);
+      if (!_.has(cache, address)) cache[address] = func.apply(this, arguments);
+      return cache[address];
     };
+    memoize.cache = {};
+    return memoize;
   };
 
   // Delays a function for the given number of milliseconds, and then calls
   // it with the arguments supplied.
   _.delay = function(func, wait) {
     var args = slice.call(arguments, 2);
-    return setTimeout(function(){ return func.apply(null, args); }, wait);
+    return setTimeout(function(){
+      return func.apply(null, args);
+    }, wait);
   };
 
   // Defers a function, scheduling it to run after the current call stack has
   // cleared.
-  _.defer = function(func) {
-    return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
-  };
+  _.defer = _.partial(_.delay, _, 1);
 
   // Returns a function, that, when invoked, will only be triggered at most once
   // during a given window of time. Normally, the throttled function will run
@@ -681,12 +782,12 @@
     var context, args, result;
     var timeout = null;
     var previous = 0;
-    options || (options = {});
+    if (!options) options = {};
     var later = function() {
       previous = options.leading === false ? 0 : _.now();
       timeout = null;
       result = func.apply(context, args);
-      context = args = null;
+      if (!timeout) context = args = null;
     };
     return function() {
       var now = _.now();
@@ -694,12 +795,14 @@
       var remaining = wait - (now - previous);
       context = this;
       args = arguments;
-      if (remaining <= 0) {
-        clearTimeout(timeout);
-        timeout = null;
+      if (remaining <= 0 || remaining > wait) {
+        if (timeout) {
+          clearTimeout(timeout);
+          timeout = null;
+        }
         previous = now;
         result = func.apply(context, args);
-        context = args = null;
+        if (!timeout) context = args = null;
       } else if (!timeout && options.trailing !== false) {
         timeout = setTimeout(later, remaining);
       }
@@ -716,13 +819,14 @@
 
     var later = function() {
       var last = _.now() - timestamp;
-      if (last < wait) {
+
+      if (last < wait && last >= 0) {
         timeout = setTimeout(later, wait - last);
       } else {
         timeout = null;
         if (!immediate) {
           result = func.apply(context, args);
-          context = args = null;
+          if (!timeout) context = args = null;
         }
       }
     };
@@ -732,9 +836,7 @@
       args = arguments;
       timestamp = _.now();
       var callNow = immediate && !timeout;
-      if (!timeout) {
-        timeout = setTimeout(later, wait);
-      }
+      if (!timeout) timeout = setTimeout(later, wait);
       if (callNow) {
         result = func.apply(context, args);
         context = args = null;
@@ -744,19 +846,6 @@
     };
   };
 
-  // Returns a function that will be executed at most one time, no matter how
-  // often you call it. Useful for lazy initialization.
-  _.once = function(func) {
-    var ran = false, memo;
-    return function() {
-      if (ran) return memo;
-      ran = true;
-      memo = func.apply(this, arguments);
-      func = null;
-      return memo;
-    };
-  };
-
   // Returns the first function passed as an argument to the second,
   // allowing you to adjust arguments, run code before and after, and
   // conditionally execute the original function.
@@ -764,20 +853,27 @@
     return _.partial(wrapper, func);
   };
 
+  // Returns a negated version of the passed-in predicate.
+  _.negate = function(predicate) {
+    return function() {
+      return !predicate.apply(this, arguments);
+    };
+  };
+
   // Returns a function that is the composition of a list of functions, each
   // consuming the return value of the function that follows.
   _.compose = function() {
-    var funcs = arguments;
+    var args = arguments;
+    var start = args.length - 1;
     return function() {
-      var args = arguments;
-      for (var i = funcs.length - 1; i >= 0; i--) {
-        args = [funcs[i].apply(this, args)];
-      }
-      return args[0];
+      var i = start;
+      var result = args[start].apply(this, arguments);
+      while (i--) result = args[i].call(this, result);
+      return result;
     };
   };
 
-  // Returns a function that will only be executed after being called N times.
+  // Returns a function that will only be executed on and after the Nth call.
   _.after = function(times, func) {
     return function() {
       if (--times < 1) {
@@ -786,16 +882,62 @@
     };
   };
 
+  // Returns a function that will only be executed up to (but not including) the Nth call.
+  _.before = function(times, func) {
+    var memo;
+    return function() {
+      if (--times > 0) {
+        memo = func.apply(this, arguments);
+      }
+      if (times <= 1) func = null;
+      return memo;
+    };
+  };
+
+  // Returns a function that will be executed at most one time, no matter how
+  // often you call it. Useful for lazy initialization.
+  _.once = _.partial(_.before, 2);
+
   // Object Functions
   // ----------------
 
-  // Retrieve the names of an object's properties.
+  // Keys in IE < 9 that won't be iterated by `for key in ...` and thus missed.
+  var hasEnumBug = !{toString: null}.propertyIsEnumerable('toString');
+  var nonEnumerableProps = ['constructor', 'valueOf', 'isPrototypeOf', 'toString',
+                      'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];
+
+  function collectNonEnumProps(obj, keys) {
+    var nonEnumIdx = nonEnumerableProps.length;
+    var proto = typeof obj.constructor === 'function' ? FuncProto : ObjProto;
+
+    while (nonEnumIdx--) {
+      var prop = nonEnumerableProps[nonEnumIdx];
+      if (prop === 'constructor' ? _.has(obj, prop) : prop in obj &&
+        obj[prop] !== proto[prop] && !_.contains(keys, prop)) {
+        keys.push(prop);
+      }
+    }
+  }
+
+  // Retrieve the names of an object's own properties.
   // Delegates to **ECMAScript 5**'s native `Object.keys`
   _.keys = function(obj) {
     if (!_.isObject(obj)) return [];
     if (nativeKeys) return nativeKeys(obj);
     var keys = [];
     for (var key in obj) if (_.has(obj, key)) keys.push(key);
+    // Ahem, IE < 9.
+    if (hasEnumBug) collectNonEnumProps(obj, keys);
+    return keys;
+  };
+
+  // Retrieve all the property names of an object.
+  _.keysIn = function(obj) {
+    if (!_.isObject(obj)) return [];
+    var keys = [];
+    for (var key in obj) keys.push(key);
+    // Ahem, IE < 9.
+    if (hasEnumBug) collectNonEnumProps(obj, keys);
     return keys;
   };
 
@@ -803,7 +945,7 @@
   _.values = function(obj) {
     var keys = _.keys(obj);
     var length = keys.length;
-    var values = new Array(length);
+    var values = Array(length);
     for (var i = 0; i < length; i++) {
       values[i] = obj[keys[i]];
     }
@@ -814,7 +956,7 @@
   _.pairs = function(obj) {
     var keys = _.keys(obj);
     var length = keys.length;
-    var pairs = new Array(length);
+    var pairs = Array(length);
     for (var i = 0; i < length; i++) {
       pairs[i] = [keys[i], obj[keys[i]]];
     }
@@ -842,49 +984,77 @@
   };
 
   // Extend a given object with all the properties in passed-in object(s).
-  _.extend = function(obj) {
-    each(slice.call(arguments, 1), function(source) {
-      if (source) {
-        for (var prop in source) {
-          obj[prop] = source[prop];
-        }
-      }
-    });
-    return obj;
+  _.extend = createAssigner(_.keysIn);
+
+  // Assigns a given object with all the own properties in the passed-in object(s)
+  // (https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign)
+  _.assign = createAssigner(_.keys);
+
+  // Returns the first key on an object that passes a predicate test
+  _.findKey = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var keys = _.keys(obj), key;
+    for (var i = 0, length = keys.length; i < length; i++) {
+      key = keys[i];
+      if (predicate(obj[key], key, obj)) return key;
+    }
   };
 
   // Return a copy of the object only containing the whitelisted properties.
-  _.pick = function(obj) {
-    var copy = {};
-    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
-    each(keys, function(key) {
-      if (key in obj) copy[key] = obj[key];
-    });
-    return copy;
+  _.pick = function(obj, iteratee, context) {
+    var result = {}, key;
+    if (obj == null) return result;
+    if (_.isFunction(iteratee)) {
+      iteratee = optimizeCb(iteratee, context);
+      for (key in obj) {
+        var value = obj[key];
+        if (iteratee(value, key, obj)) result[key] = value;
+      }
+    } else {
+      var keys = flatten(arguments, false, false, 1);
+      obj = new Object(obj);
+      for (var i = 0, length = keys.length; i < length; i++) {
+        key = keys[i];
+        if (key in obj) result[key] = obj[key];
+      }
+    }
+    return result;
   };
 
    // Return a copy of the object without the blacklisted properties.
-  _.omit = function(obj) {
-    var copy = {};
-    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
-    for (var key in obj) {
-      if (!_.contains(keys, key)) copy[key] = obj[key];
+  _.omit = function(obj, iteratee, context) {
+    if (_.isFunction(iteratee)) {
+      iteratee = _.negate(iteratee);
+    } else {
+      var keys = _.map(flatten(arguments, false, false, 1), String);
+      iteratee = function(value, key) {
+        return !_.contains(keys, key);
+      };
     }
-    return copy;
+    return _.pick(obj, iteratee, context);
   };
 
   // Fill in a given object with default properties.
   _.defaults = function(obj) {
-    each(slice.call(arguments, 1), function(source) {
-      if (source) {
-        for (var prop in source) {
-          if (obj[prop] === void 0) obj[prop] = source[prop];
-        }
+    if (!_.isObject(obj)) return obj;
+    for (var i = 1, length = arguments.length; i < length; i++) {
+      var source = arguments[i];
+      for (var prop in source) {
+        if (obj[prop] === void 0) obj[prop] = source[prop];
       }
-    });
+    }
     return obj;
   };
 
+  // Creates an object that inherits from the given prototype object.
+  // If additional properties are provided then they will be added to the
+  // created object.
+  _.create = function(prototype, props) {
+    var result = baseCreate(prototype);
+    if (props) _.assign(result, props);
+    return result;
+  };
+
   // Create a (shallow-cloned) duplicate of an object.
   _.clone = function(obj) {
     if (!_.isObject(obj)) return obj;
@@ -903,7 +1073,7 @@
   var eq = function(a, b, aStack, bStack) {
     // Identical objects are equal. `0 === -0`, but they aren't identical.
     // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
-    if (a === b) return a !== 0 || 1 / a == 1 / b;
+    if (a === b) return a !== 0 || 1 / a === 1 / b;
     // A strict comparison is necessary because `null == undefined`.
     if (a == null || b == null) return a === b;
     // Unwrap any wrapped objects.
@@ -911,84 +1081,80 @@
     if (b instanceof _) b = b._wrapped;
     // Compare `[[Class]]` names.
     var className = toString.call(a);
-    if (className != toString.call(b)) return false;
+    if (className !== toString.call(b)) return false;
     switch (className) {
-      // Strings, numbers, dates, and booleans are compared by value.
+      // Strings, numbers, regular expressions, dates, and booleans are compared by value.
+      case '[object RegExp]':
+      // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
       case '[object String]':
         // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
         // equivalent to `new String("5")`.
-        return a == String(b);
+        return '' + a === '' + b;
       case '[object Number]':
-        // `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
-        // other numeric values.
-        return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
+        // `NaN`s are equivalent, but non-reflexive.
+        // Object(NaN) is equivalent to NaN
+        if (+a !== +a) return +b !== +b;
+        // An `egal` comparison is performed for other numeric values.
+        return +a === 0 ? 1 / +a === 1 / b : +a === +b;
       case '[object Date]':
       case '[object Boolean]':
         // Coerce dates and booleans to numeric primitive values. Dates are compared by their
         // millisecond representations. Note that invalid dates with millisecond representations
         // of `NaN` are not equivalent.
-        return +a == +b;
-      // RegExps are compared by their source patterns and flags.
-      case '[object RegExp]':
-        return a.source == b.source &&
-               a.global == b.global &&
-               a.multiline == b.multiline &&
-               a.ignoreCase == b.ignoreCase;
+        return +a === +b;
+    }
+
+    var areArrays = className === '[object Array]';
+    if (!areArrays) {
+      if (typeof a != 'object' || typeof b != 'object') return false;
+
+      // Objects with different constructors are not equivalent, but `Object`s or `Array`s
+      // from different frames are.
+      var aCtor = a.constructor, bCtor = b.constructor;
+      if (aCtor !== bCtor && !(_.isFunction(aCtor) && aCtor instanceof aCtor &&
+                               _.isFunction(bCtor) && bCtor instanceof bCtor)
+                          && ('constructor' in a && 'constructor' in b)) {
+        return false;
+      }
     }
-    if (typeof a != 'object' || typeof b != 'object') return false;
     // Assume equality for cyclic structures. The algorithm for detecting cyclic
     // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
     var length = aStack.length;
     while (length--) {
       // Linear search. Performance is inversely proportional to the number of
       // unique nested structures.
-      if (aStack[length] == a) return bStack[length] == b;
-    }
-    // Objects with different constructors are not equivalent, but `Object`s
-    // from different frames are.
-    var aCtor = a.constructor, bCtor = b.constructor;
-    if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
-                             _.isFunction(bCtor) && (bCtor instanceof bCtor))
-                        && ('constructor' in a && 'constructor' in b)) {
-      return false;
+      if (aStack[length] === a) return bStack[length] === b;
     }
+
     // Add the first object to the stack of traversed objects.
     aStack.push(a);
     bStack.push(b);
-    var size = 0, result = true;
+
     // Recursively compare objects and arrays.
-    if (className == '[object Array]') {
+    if (areArrays) {
       // Compare array lengths to determine if a deep comparison is necessary.
-      size = a.length;
-      result = size == b.length;
-      if (result) {
-        // Deep compare the contents, ignoring non-numeric properties.
-        while (size--) {
-          if (!(result = eq(a[size], b[size], aStack, bStack))) break;
-        }
+      length = a.length;
+      if (length !== b.length) return false;
+      // Deep compare the contents, ignoring non-numeric properties.
+      while (length--) {
+        if (!eq(a[length], b[length], aStack, bStack)) return false;
       }
     } else {
       // Deep compare objects.
-      for (var key in a) {
-        if (_.has(a, key)) {
-          // Count the expected number of properties.
-          size++;
-          // Deep compare each member.
-          if (!(result = _.has(b, key) && eq(a[key], b[key], aStack, bStack))) break;
-        }
-      }
-      // Ensure that both objects contain the same number of properties.
-      if (result) {
-        for (key in b) {
-          if (_.has(b, key) && !(size--)) break;
-        }
-        result = !size;
+      var keys = _.keys(a), key;
+      length = keys.length;
+      // Ensure that both objects contain the same number of properties before comparing deep equality.
+      if (_.keys(b).length !== length) return false;
+      while (length--) {
+        // Deep compare each member
+        key = keys[length];
+        if (!(_.has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
       }
     }
     // Remove the first object from the stack of traversed objects.
     aStack.pop();
     bStack.pop();
-    return result;
+    return true;
   };
 
   // Perform a deep comparison to check if two objects are equal.
@@ -1000,7 +1166,7 @@
   // An "empty" object has no enumerable own-properties.
   _.isEmpty = function(obj) {
     if (obj == null) return true;
-    if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
+    if (_.isArray(obj) || _.isString(obj) || _.isArguments(obj)) return obj.length === 0;
     for (var key in obj) if (_.has(obj, key)) return false;
     return true;
   };
@@ -1013,33 +1179,35 @@
   // Is a given value an array?
   // Delegates to ECMA5's native Array.isArray
   _.isArray = nativeIsArray || function(obj) {
-    return toString.call(obj) == '[object Array]';
+    return toString.call(obj) === '[object Array]';
   };
 
   // Is a given variable an object?
   _.isObject = function(obj) {
-    return obj === Object(obj);
+    var type = typeof obj;
+    return type === 'function' || type === 'object' && !!obj;
   };
 
-  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.
-  each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) {
+  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
+  _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
     _['is' + name] = function(obj) {
-      return toString.call(obj) == '[object ' + name + ']';
+      return toString.call(obj) === '[object ' + name + ']';
     };
   });
 
-  // Define a fallback version of the method in browsers (ahem, IE), where
+  // Define a fallback version of the method in browsers (ahem, IE < 9), where
   // there isn't any inspectable "Arguments" type.
   if (!_.isArguments(arguments)) {
     _.isArguments = function(obj) {
-      return !!(obj && _.has(obj, 'callee'));
+      return _.has(obj, 'callee');
     };
   }
 
-  // Optimize `isFunction` if appropriate.
-  if (typeof (/./) !== 'function') {
+  // Optimize `isFunction` if appropriate. Work around an IE 11 bug (#1621).
+  // Work around a Safari 8 bug (#1929)
+  if (typeof /./ != 'function' && typeof Int8Array != 'object') {
     _.isFunction = function(obj) {
-      return typeof obj === 'function';
+      return typeof obj == 'function' || false;
     };
   }
 
@@ -1050,12 +1218,12 @@
 
   // Is the given value `NaN`? (NaN is the only number which does not equal itself).
   _.isNaN = function(obj) {
-    return _.isNumber(obj) && obj != +obj;
+    return _.isNumber(obj) && obj !== +obj;
   };
 
   // Is a given value a boolean?
   _.isBoolean = function(obj) {
-    return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
+    return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
   };
 
   // Is a given value equal to null?
@@ -1071,7 +1239,7 @@
   // Shortcut function for checking if an object has a given property directly
   // on itself (in other words, not on a prototype).
   _.has = function(obj, key) {
-    return hasOwnProperty.call(obj, key);
+    return obj != null && hasOwnProperty.call(obj, key);
   };
 
   // Utility Functions
@@ -1084,39 +1252,64 @@
     return this;
   };
 
-  // Keep the identity function around for default iterators.
+  // Keep the identity function around for default iteratees.
   _.identity = function(value) {
     return value;
   };
 
+  // Predicate-generating functions. Often useful outside of Underscore.
   _.constant = function(value) {
-    return function () {
+    return function() {
       return value;
     };
   };
 
+  _.noop = function(){};
+
   _.property = function(key) {
     return function(obj) {
+      return obj == null ? void 0 : obj[key];
+    };
+  };
+
+  // Generates a function for a given object that returns a given property (including those of ancestors)
+  _.propertyOf = function(obj) {
+    return obj == null ? function(){} : function(key) {
       return obj[key];
     };
   };
 
   // Returns a predicate for checking whether an object has a given set of `key:value` pairs.
   _.matches = function(attrs) {
+    var pairs = _.pairs(attrs), length = pairs.length;
     return function(obj) {
-      if (obj === attrs) return true; //avoid comparing an object to itself.
-      for (var key in attrs) {
-        if (attrs[key] !== obj[key])
-          return false;
+      if (obj == null) return !length;
+      obj = new Object(obj);
+      for (var i = 0; i < length; i++) {
+        var pair = pairs[i], key = pair[0];
+        if (pair[1] !== obj[key] || !(key in obj)) return false;
       }
       return true;
+    };
+  };
+
+  // Default internal comparator for determining whether a is greater (1),
+  // equal (0) or less than (-1) some object b
+  _.comparator = function(a, b) {
+    if (a === b) return 0;
+    var isAComparable = a >= a, isBComparable = b >= b;
+    if (isAComparable || isBComparable) {
+      if (isAComparable && !isBComparable) return -1;
+      if (isBComparable && !isAComparable) return 1;
     }
+    return a > b ? 1 : (b > a) ? -1 : 0;
   };
 
   // Run a function **n** times.
-  _.times = function(n, iterator, context) {
+  _.times = function(n, iteratee, context) {
     var accum = Array(Math.max(0, n));
-    for (var i = 0; i < n; i++) accum[i] = iterator.call(context, i);
+    iteratee = optimizeCb(iteratee, context, 1);
+    for (var i = 0; i < n; i++) accum[i] = iteratee(i);
     return accum;
   };
 
@@ -1130,56 +1323,48 @@
   };
 
   // A (possibly faster) way to get the current timestamp as an integer.
-  _.now = Date.now || function() { return new Date().getTime(); };
-
-  // List of HTML entities for escaping.
-  var entityMap = {
-    escape: {
-      '&': '&amp;',
-      '<': '&lt;',
-      '>': '&gt;',
-      '"': '&quot;',
-      "'": '&#x27;'
-    }
+  _.now = Date.now || function() {
+    return new Date().getTime();
   };
-  entityMap.unescape = _.invert(entityMap.escape);
 
-  // Regexes containing the keys and values listed immediately above.
-  var entityRegexes = {
-    escape:   new RegExp('[' + _.keys(entityMap.escape).join('') + ']', 'g'),
-    unescape: new RegExp('(' + _.keys(entityMap.unescape).join('|') + ')', 'g')
+   // List of HTML entities for escaping.
+  var escapeMap = {
+    '&': '&amp;',
+    '<': '&lt;',
+    '>': '&gt;',
+    '"': '&quot;',
+    "'": '&#x27;',
+    '`': '&#x60;'
   };
+  var unescapeMap = _.invert(escapeMap);
 
   // Functions for escaping and unescaping strings to/from HTML interpolation.
-  _.each(['escape', 'unescape'], function(method) {
-    _[method] = function(string) {
-      if (string == null) return '';
-      return ('' + string).replace(entityRegexes[method], function(match) {
-        return entityMap[method][match];
-      });
+  var createEscaper = function(map) {
+    var escaper = function(match) {
+      return map[match];
     };
-  });
+    // Regexes for identifying a key that needs to be escaped
+    var source = '(?:' + _.keys(map).join('|') + ')';
+    var testRegexp = RegExp(source);
+    var replaceRegexp = RegExp(source, 'g');
+    return function(string) {
+      string = string == null ? '' : '' + string;
+      return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
+    };
+  };
+  _.escape = createEscaper(escapeMap);
+  _.unescape = createEscaper(unescapeMap);
 
   // If the value of the named `property` is a function then invoke it with the
   // `object` as context; otherwise, return it.
-  _.result = function(object, property) {
-    if (object == null) return void 0;
-    var value = object[property];
+  _.result = function(object, property, fallback) {
+    var value = object == null ? void 0 : object[property];
+    if (value === void 0) {
+      value = fallback;
+    }
     return _.isFunction(value) ? value.call(object) : value;
   };
 
-  // Add your own custom functions to the Underscore object.
-  _.mixin = function(obj) {
-    each(_.functions(obj), function(name) {
-      var func = _[name] = obj[name];
-      _.prototype[name] = function() {
-        var args = [this._wrapped];
-        push.apply(args, arguments);
-        return result.call(this, func.apply(_, args));
-      };
-    });
-  };
-
   // Generate a unique integer id (unique within the entire client session).
   // Useful for temporary DOM ids.
   var idCounter = 0;
@@ -1208,22 +1393,26 @@
     '\\':     '\\',
     '\r':     'r',
     '\n':     'n',
-    '\t':     't',
     '\u2028': 'u2028',
     '\u2029': 'u2029'
   };
 
-  var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
+  var escaper = /\\|'|\r|\n|\u2028|\u2029/g;
+
+  var escapeChar = function(match) {
+    return '\\' + escapes[match];
+  };
 
   // JavaScript micro-templating, similar to John Resig's implementation.
   // Underscore templating handles arbitrary delimiters, preserves whitespace,
   // and correctly escapes quotes within interpolated code.
-  _.template = function(text, data, settings) {
-    var render;
+  // NB: `oldSettings` only exists for backwards compatibility.
+  _.template = function(text, settings, oldSettings) {
+    if (!settings && oldSettings) settings = oldSettings;
     settings = _.defaults({}, settings, _.templateSettings);
 
     // Combine delimiters into one regular expression via alternation.
-    var matcher = new RegExp([
+    var matcher = RegExp([
       (settings.escape || noMatch).source,
       (settings.interpolate || noMatch).source,
       (settings.evaluate || noMatch).source
@@ -1233,19 +1422,18 @@
     var index = 0;
     var source = "__p+='";
     text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
-      source += text.slice(index, offset)
-        .replace(escaper, function(match) { return '\\' + escapes[match]; });
+      source += text.slice(index, offset).replace(escaper, escapeChar);
+      index = offset + match.length;
 
       if (escape) {
         source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
-      }
-      if (interpolate) {
+      } else if (interpolate) {
         source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
-      }
-      if (evaluate) {
+      } else if (evaluate) {
         source += "';\n" + evaluate + "\n__p+='";
       }
-      index = offset + match.length;
+
+      // Adobe VMs need the match returned to produce the correct offest.
       return match;
     });
     source += "';\n";
@@ -1255,29 +1443,31 @@
 
     source = "var __t,__p='',__j=Array.prototype.join," +
       "print=function(){__p+=__j.call(arguments,'');};\n" +
-      source + "return __p;\n";
+      source + 'return __p;\n';
 
     try {
-      render = new Function(settings.variable || 'obj', '_', source);
+      var render = new Function(settings.variable || 'obj', '_', source);
     } catch (e) {
       e.source = source;
       throw e;
     }
 
-    if (data) return render(data, _);
     var template = function(data) {
       return render.call(this, data, _);
     };
 
-    // Provide the compiled function source as a convenience for precompilation.
-    template.source = 'function(' + (settings.variable || 'obj') + '){\n' + source + '}';
+    // Provide the compiled source as a convenience for precompilation.
+    var argument = settings.variable || 'obj';
+    template.source = 'function(' + argument + '){\n' + source + '}';
 
     return template;
   };
 
-  // Add a "chain" function, which will delegate to the wrapper.
+  // Add a "chain" function. Start chaining a wrapped Underscore object.
   _.chain = function(obj) {
-    return _(obj).chain();
+    var instance = _(obj);
+    instance._chain = true;
+    return instance;
   };
 
   // OOP
@@ -1287,46 +1477,48 @@
   // underscore functions. Wrapped objects may be chained.
 
   // Helper function to continue chaining intermediate results.
-  var result = function(obj) {
-    return this._chain ? _(obj).chain() : obj;
+  var result = function(instance, obj) {
+    return instance._chain ? _(obj).chain() : obj;
+  };
+
+  // Add your own custom functions to the Underscore object.
+  _.mixin = function(obj) {
+    _.each(_.functions(obj), function(name) {
+      var func = _[name] = obj[name];
+      _.prototype[name] = function() {
+        var args = [this._wrapped];
+        push.apply(args, arguments);
+        return result(this, func.apply(_, args));
+      };
+    });
   };
 
   // Add all of the Underscore functions to the wrapper object.
   _.mixin(_);
 
   // Add all mutator Array functions to the wrapper.
-  each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
+  _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
     var method = ArrayProto[name];
     _.prototype[name] = function() {
       var obj = this._wrapped;
       method.apply(obj, arguments);
-      if ((name == 'shift' || name == 'splice') && obj.length === 0) delete obj[0];
-      return result.call(this, obj);
+      if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
+      return result(this, obj);
     };
   });
 
   // Add all accessor Array functions to the wrapper.
-  each(['concat', 'join', 'slice'], function(name) {
+  _.each(['concat', 'join', 'slice'], function(name) {
     var method = ArrayProto[name];
     _.prototype[name] = function() {
-      return result.call(this, method.apply(this._wrapped, arguments));
+      return result(this, method.apply(this._wrapped, arguments));
     };
   });
 
-  _.extend(_.prototype, {
-
-    // Start chaining a wrapped Underscore object.
-    chain: function() {
-      this._chain = true;
-      return this;
-    },
-
-    // Extracts the result from a wrapped and chained object.
-    value: function() {
-      return this._wrapped;
-    }
-
-  });
+  // Extracts the result from a wrapped and chained object.
+  _.prototype.value = function() {
+    return this._wrapped;
+  };
 
   // AMD registration happens at the end for compatibility with AMD loaders
   // that may not enforce next-turn semantics on modules. Even though general
@@ -1340,4 +1532,4 @@
       return _;
     });
   }
-}).call(this);
+}.call(this));
\ No newline at end of file

From 3aca1201a4ca190c228ba40ff530d479c3200206 Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Sat, 3 Jan 2015 21:11:43 +0000
Subject: [PATCH 09/11] use _.matches in `where`

updated code to match changes to backbone.js
---
 backbone.js | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/backbone.js b/backbone.js
index 703307417..2a0d1f1fc 100644
--- a/backbone.js
+++ b/backbone.js
@@ -878,14 +878,10 @@
     // Return models with matching attributes. Useful for simple cases of
     // `filter`.
     where: function(attrs, first) {
-      if (_.isEmpty(attrs)) {
-        return first ? void 0 : [];
-      } else if (!_.isEqual(_.keys(attrs), [this.comparator])) {
+      if (_.isEmpty(attrs) || !_.isEqual(_.keys(attrs), [this.comparator])) {
+        var matches = _.matches(attrs);
         return this[first ? 'find' : 'filter'](function(model) {
-          for (var key in attrs) {
-            if (attrs[key] !== model.get(key)) return false;
-          }
-          return true;
+          return matches(model.attributes);
         });
       } else if (first) {
         return this.at(this.search(attrs[this.comparator]));

From 60038bbc6a953fcac1cc8355518615b79e24adac Mon Sep 17 00:00:00 2001
From: Joshua Bambrick <jpbambrick@gmail.com>
Date: Fri, 17 Apr 2015 16:17:40 +0100
Subject: [PATCH 10/11] use local comparator, reset underscore.js version

---
 backbone.js               |   16 +-
 test/vendor/underscore.js | 1208 ++++++++++++++++---------------------
 2 files changed, 522 insertions(+), 702 deletions(-)

diff --git a/backbone.js b/backbone.js
index 2a0d1f1fc..668a0db66 100644
--- a/backbone.js
+++ b/backbone.js
@@ -629,6 +629,18 @@
   var setOptions = {add: true, remove: true, merge: true};
   var addOptions = {add: true, remove: false};
 
+  // Compare two values, in a `sort`-consistent way
+  var compareVals = function(a, b) {
+    if (a === b) return 0;
+    var isAComparable = a >= a, isBComparable = b >= b;
+    if (isAComparable || isBComparable) {
+      if (isAComparable && !isBComparable) return -1;
+      if (isBComparable && !isAComparable) return 1;
+    }
+    return a > b ? 1 : (b > a) ? -1 : 0;
+  };
+
+
   // Define the Collection's inheritable methods.
   _.extend(Collection.prototype, Events, {
 
@@ -843,14 +855,14 @@
           compare = _.bind(this.comparator, this, toFind);
         } else {
           compare = _.bind(function (valResult, model) {
-            return _.comparator(valResult, this.comparator(model));
+            return compareVals(valResult, this.comparator(model));
           }, this, this.comparator(toFind));
         }
       } else {
         // `comparator` is a string indicating the model property used to sort
         // `toFind` is the value sought.
         compare = _.bind(function (model) {
-          return _.comparator(toFind, model.get(this.comparator));
+          return compareVals(toFind, model.get(this.comparator));
         }, this);
       }
 
diff --git a/test/vendor/underscore.js b/test/vendor/underscore.js
index 62bcf9006..00d3deb92 100644
--- a/test/vendor/underscore.js
+++ b/test/vendor/underscore.js
@@ -1,4 +1,4 @@
-//     Underscore.js 1.7.0
+//     Underscore.js 1.6.0
 //     http://underscorejs.org
 //     (c) 2009-2014 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 //     Underscore may be freely distributed under the MIT license.
@@ -14,6 +14,9 @@
   // Save the previous value of the `_` variable.
   var previousUnderscore = root._;
 
+  // Establish the object that gets returned to break out of a loop iteration.
+  var breaker = {};
+
   // Save bytes in the minified (but not gzipped) version:
   var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
 
@@ -21,19 +24,25 @@
   var
     push             = ArrayProto.push,
     slice            = ArrayProto.slice,
+    concat           = ArrayProto.concat,
     toString         = ObjProto.toString,
     hasOwnProperty   = ObjProto.hasOwnProperty;
 
   // All **ECMAScript 5** native function implementations that we hope to use
   // are declared here.
   var
+    nativeForEach      = ArrayProto.forEach,
+    nativeMap          = ArrayProto.map,
+    nativeReduce       = ArrayProto.reduce,
+    nativeReduceRight  = ArrayProto.reduceRight,
+    nativeFilter       = ArrayProto.filter,
+    nativeEvery        = ArrayProto.every,
+    nativeSome         = ArrayProto.some,
+    nativeIndexOf      = ArrayProto.indexOf,
+    nativeLastIndexOf  = ArrayProto.lastIndexOf,
     nativeIsArray      = Array.isArray,
     nativeKeys         = Object.keys,
-    nativeBind         = FuncProto.bind,
-    nativeCreate       = Object.create;
-
-  // Reusable constructor function for prototype setting.
-  var Ctor = function(){};
+    nativeBind         = FuncProto.bind;
 
   // Create a safe reference to the Underscore object for use below.
   var _ = function(obj) {
@@ -44,7 +53,8 @@
 
   // Export the Underscore object for **Node.js**, with
   // backwards-compatibility for the old `require()` API. If we're in
-  // the browser, add `_` as a global object.
+  // the browser, add `_` as a global object via a string identifier,
+  // for Closure Compiler "advanced" mode.
   if (typeof exports !== 'undefined') {
     if (typeof module !== 'undefined' && module.exports) {
       exports = module.exports = _;
@@ -55,235 +65,161 @@
   }
 
   // Current version.
-  _.VERSION = '1.7.0';
-
-  // Internal function that returns an efficient (for current engines) version
-  // of the passed-in callback, to be repeatedly applied in other Underscore
-  // functions.
-  var optimizeCb = function(func, context, argCount) {
-    if (context === void 0) return func;
-    switch (argCount == null ? 3 : argCount) {
-      case 1: return function(value) {
-        return func.call(context, value);
-      };
-      case 2: return function(value, other) {
-        return func.call(context, value, other);
-      };
-      case 3: return function(value, index, collection) {
-        return func.call(context, value, index, collection);
-      };
-      case 4: return function(accumulator, value, index, collection) {
-        return func.call(context, accumulator, value, index, collection);
-      };
-    }
-    return function() {
-      return func.apply(context, arguments);
-    };
-  };
-
-  // A mostly-internal function to generate callbacks that can be applied
-  // to each element in a collection, returning the desired result — either
-  // identity, an arbitrary callback, a property matcher, or a property accessor.
-  var cb = function(value, context, argCount) {
-    if (value == null) return _.identity;
-    if (_.isFunction(value)) return optimizeCb(value, context, argCount);
-    if (_.isObject(value)) return _.matches(value);
-    return _.property(value);
-  };
-  _.iteratee = function(value, context) {
-    return cb(value, context, Infinity);
-  };
-
-  // An internal function for creating assigner functions.
-  var createAssigner = function(keysFunc) {
-    return function(obj) {
-      var length = arguments.length;
-      if (length < 2 || obj == null) return obj;
-      for (var index = 0; index < length; index++) {
-        var source = arguments[index],
-            keys = keysFunc(source),
-            l = keys.length;
-        for (var i = 0; i < l; i++) {
-          var key = keys[i];
-          obj[key] = source[key];
-        }
-      }
-      return obj;
-    };
-  };
-
-  // An internal function for creating a new object that inherits from another.
-  var baseCreate = function(prototype) {
-    if (!_.isObject(prototype)) return {};
-    if (nativeCreate) return nativeCreate(prototype);
-    Ctor.prototype = prototype;
-    var result = new Ctor;
-    Ctor.prototype = null;
-    return result;
-  };
+  _.VERSION = '1.6.0';
 
   // Collection Functions
   // --------------------
 
   // The cornerstone, an `each` implementation, aka `forEach`.
-  // Handles raw objects in addition to array-likes. Treats all
-  // sparse array-likes as if they were dense.
-  _.each = _.forEach = function(obj, iteratee, context) {
+  // Handles objects with the built-in `forEach`, arrays, and raw objects.
+  // Delegates to **ECMAScript 5**'s native `forEach` if available.
+  var each = _.each = _.forEach = function(obj, iterator, context) {
     if (obj == null) return obj;
-    iteratee = optimizeCb(iteratee, context);
-    var i, length = obj.length;
-    if (length === +length) {
-      for (i = 0; i < length; i++) {
-        iteratee(obj[i], i, obj);
+    if (nativeForEach && obj.forEach === nativeForEach) {
+      obj.forEach(iterator, context);
+    } else if (obj.length === +obj.length) {
+      for (var i = 0, length = obj.length; i < length; i++) {
+        if (iterator.call(context, obj[i], i, obj) === breaker) return;
       }
     } else {
       var keys = _.keys(obj);
-      for (i = 0, length = keys.length; i < length; i++) {
-        iteratee(obj[keys[i]], keys[i], obj);
+      for (var i = 0, length = keys.length; i < length; i++) {
+        if (iterator.call(context, obj[keys[i]], keys[i], obj) === breaker) return;
       }
     }
     return obj;
   };
 
-  // Return the results of applying the iteratee to each element.
-  _.map = _.collect = function(obj, iteratee, context) {
-    if (obj == null) return [];
-    iteratee = cb(iteratee, context);
-    var keys = obj.length !== +obj.length && _.keys(obj),
-        length = (keys || obj).length,
-        results = Array(length),
-        currentKey;
-    for (var index = 0; index < length; index++) {
-      currentKey = keys ? keys[index] : index;
-      results[index] = iteratee(obj[currentKey], currentKey, obj);
-    }
+  // Return the results of applying the iterator to each element.
+  // Delegates to **ECMAScript 5**'s native `map` if available.
+  _.map = _.collect = function(obj, iterator, context) {
+    var results = [];
+    if (obj == null) return results;
+    if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
+    each(obj, function(value, index, list) {
+      results.push(iterator.call(context, value, index, list));
+    });
     return results;
   };
 
+  var reduceError = 'Reduce of empty array with no initial value';
+
   // **Reduce** builds up a single result from a list of values, aka `inject`,
-  // or `foldl`.
-  _.reduce = _.foldl = _.inject = function(obj, iteratee, memo, context) {
+  // or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
+  _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
+    var initial = arguments.length > 2;
     if (obj == null) obj = [];
-    iteratee = optimizeCb(iteratee, context, 4);
-    var keys = obj.length !== +obj.length && _.keys(obj),
-        length = (keys || obj).length,
-        index = 0, currentKey;
-    if (arguments.length < 3) {
-      memo = obj[keys ? keys[index++] : index++];
-    }
-    for (; index < length; index++) {
-      currentKey = keys ? keys[index] : index;
-      memo = iteratee(memo, obj[currentKey], currentKey, obj);
+    if (nativeReduce && obj.reduce === nativeReduce) {
+      if (context) iterator = _.bind(iterator, context);
+      return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
     }
+    each(obj, function(value, index, list) {
+      if (!initial) {
+        memo = value;
+        initial = true;
+      } else {
+        memo = iterator.call(context, memo, value, index, list);
+      }
+    });
+    if (!initial) throw new TypeError(reduceError);
     return memo;
   };
 
   // The right-associative version of reduce, also known as `foldr`.
-  _.reduceRight = _.foldr = function(obj, iteratee, memo, context) {
+  // Delegates to **ECMAScript 5**'s native `reduceRight` if available.
+  _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
+    var initial = arguments.length > 2;
     if (obj == null) obj = [];
-    iteratee = optimizeCb(iteratee, context, 4);
-    var keys = obj.length !== + obj.length && _.keys(obj),
-        index = (keys || obj).length,
-        currentKey;
-    if (arguments.length < 3) {
-      memo = obj[keys ? keys[--index] : --index];
+    if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
+      if (context) iterator = _.bind(iterator, context);
+      return initial ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
     }
-    while (index-- > 0) {
-      currentKey = keys ? keys[index] : index;
-      memo = iteratee(memo, obj[currentKey], currentKey, obj);
+    var length = obj.length;
+    if (length !== +length) {
+      var keys = _.keys(obj);
+      length = keys.length;
     }
-    return memo;
-  };
-
-  // **Transform** is an alternative to reduce that transforms `obj` to a new
-  // `accumulator` object.
-  _.transform = function(obj, iteratee, accumulator, context) {
-    if (accumulator == null) {
-      if (_.isArray(obj)) {
-        accumulator = [];
-      } else if (_.isObject(obj)) {
-        var Ctor = obj.constructor;
-        accumulator = baseCreate(typeof Ctor == 'function' && Ctor.prototype);
+    each(obj, function(value, index, list) {
+      index = keys ? keys[--length] : --length;
+      if (!initial) {
+        memo = obj[index];
+        initial = true;
       } else {
-        accumulator = {};
+        memo = iterator.call(context, memo, obj[index], index, list);
       }
-    }
-    if (obj == null) return accumulator;
-    iteratee = optimizeCb(iteratee, context, 4);
-    var keys = obj.length !== +obj.length && _.keys(obj),
-      length = (keys || obj).length,
-      index, currentKey;
-    for (index = 0; index < length; index++) {
-      currentKey = keys ? keys[index] : index;
-      if (iteratee(accumulator, obj[currentKey], currentKey, obj) === false) break;
-    }
-    return accumulator;
+    });
+    if (!initial) throw new TypeError(reduceError);
+    return memo;
   };
 
   // Return the first value which passes a truth test. Aliased as `detect`.
   _.find = _.detect = function(obj, predicate, context) {
-    var key;
-    if (obj.length === +obj.length) {
-      key = _.findIndex(obj, predicate, context);
-    } else {
-      key = _.findKey(obj, predicate, context);
-    }
-    if (key !== void 0 && key !== -1) return obj[key];
+    var result;
+    any(obj, function(value, index, list) {
+      if (predicate.call(context, value, index, list)) {
+        result = value;
+        return true;
+      }
+    });
+    return result;
   };
 
   // Return all the elements that pass a truth test.
+  // Delegates to **ECMAScript 5**'s native `filter` if available.
   // Aliased as `select`.
   _.filter = _.select = function(obj, predicate, context) {
     var results = [];
     if (obj == null) return results;
-    predicate = cb(predicate, context);
-    _.each(obj, function(value, index, list) {
-      if (predicate(value, index, list)) results.push(value);
+    if (nativeFilter && obj.filter === nativeFilter) return obj.filter(predicate, context);
+    each(obj, function(value, index, list) {
+      if (predicate.call(context, value, index, list)) results.push(value);
     });
     return results;
   };
 
   // Return all the elements for which a truth test fails.
   _.reject = function(obj, predicate, context) {
-    return _.filter(obj, _.negate(cb(predicate)), context);
+    return _.filter(obj, function(value, index, list) {
+      return !predicate.call(context, value, index, list);
+    }, context);
   };
 
   // Determine whether all of the elements match a truth test.
+  // Delegates to **ECMAScript 5**'s native `every` if available.
   // Aliased as `all`.
   _.every = _.all = function(obj, predicate, context) {
-    if (obj == null) return true;
-    predicate = cb(predicate, context);
-    var keys = obj.length !== +obj.length && _.keys(obj),
-        length = (keys || obj).length,
-        index, currentKey;
-    for (index = 0; index < length; index++) {
-      currentKey = keys ? keys[index] : index;
-      if (!predicate(obj[currentKey], currentKey, obj)) return false;
-    }
-    return true;
+    predicate || (predicate = _.identity);
+    var result = true;
+    if (obj == null) return result;
+    if (nativeEvery && obj.every === nativeEvery) return obj.every(predicate, context);
+    each(obj, function(value, index, list) {
+      if (!(result = result && predicate.call(context, value, index, list))) return breaker;
+    });
+    return !!result;
   };
 
   // Determine if at least one element in the object matches a truth test.
+  // Delegates to **ECMAScript 5**'s native `some` if available.
   // Aliased as `any`.
-  _.some = _.any = function(obj, predicate, context) {
-    if (obj == null) return false;
-    predicate = cb(predicate, context);
-    var keys = obj.length !== +obj.length && _.keys(obj),
-        length = (keys || obj).length,
-        index, currentKey;
-    for (index = 0; index < length; index++) {
-      currentKey = keys ? keys[index] : index;
-      if (predicate(obj[currentKey], currentKey, obj)) return true;
-    }
-    return false;
+  var any = _.some = _.any = function(obj, predicate, context) {
+    predicate || (predicate = _.identity);
+    var result = false;
+    if (obj == null) return result;
+    if (nativeSome && obj.some === nativeSome) return obj.some(predicate, context);
+    each(obj, function(value, index, list) {
+      if (result || (result = predicate.call(context, value, index, list))) return breaker;
+    });
+    return !!result;
   };
 
   // Determine if the array or object contains a given value (using `===`).
-  // Aliased as `includes` and `include`.
-  _.contains = _.includes = _.include = function(obj, target, fromIndex) {
+  // Aliased as `include`.
+  _.contains = _.include = function(obj, target) {
     if (obj == null) return false;
-    if (obj.length !== +obj.length) obj = _.values(obj);
-    return _.indexOf(obj, target, typeof fromIndex == 'number' && fromIndex) >= 0;
+    if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
+    return any(obj, function(value) {
+      return value === target;
+    });
   };
 
   // Invoke a method (with arguments) on every item in a collection.
@@ -312,67 +248,51 @@
     return _.find(obj, _.matches(attrs));
   };
 
-  // Return the maximum element (or element-based computation).
-  _.max = function(obj, iteratee, context) {
-    var result = -Infinity, lastComputed = -Infinity,
-        value, computed;
-    if (iteratee == null && obj != null) {
-      obj = obj.length === +obj.length ? obj : _.values(obj);
-      for (var i = 0, length = obj.length; i < length; i++) {
-        value = obj[i];
-        if (value > result) {
-          result = value;
-        }
-      }
-    } else {
-      iteratee = cb(iteratee, context);
-      _.each(obj, function(value, index, list) {
-        computed = iteratee(value, index, list);
-        if (computed > lastComputed || computed === -Infinity && result === -Infinity) {
-          result = value;
-          lastComputed = computed;
-        }
-      });
+  // Return the maximum element or (element-based computation).
+  // Can't optimize arrays of integers longer than 65,535 elements.
+  // See [WebKit Bug 80797](https://bugs.webkit.org/show_bug.cgi?id=80797)
+  _.max = function(obj, iterator, context) {
+    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
+      return Math.max.apply(Math, obj);
     }
+    var result = -Infinity, lastComputed = -Infinity;
+    each(obj, function(value, index, list) {
+      var computed = iterator ? iterator.call(context, value, index, list) : value;
+      if (computed > lastComputed) {
+        result = value;
+        lastComputed = computed;
+      }
+    });
     return result;
   };
 
   // Return the minimum element (or element-based computation).
-  _.min = function(obj, iteratee, context) {
-    var result = Infinity, lastComputed = Infinity,
-        value, computed;
-    if (iteratee == null && obj != null) {
-      obj = obj.length === +obj.length ? obj : _.values(obj);
-      for (var i = 0, length = obj.length; i < length; i++) {
-        value = obj[i];
-        if (value < result) {
-          result = value;
-        }
-      }
-    } else {
-      iteratee = cb(iteratee, context);
-      _.each(obj, function(value, index, list) {
-        computed = iteratee(value, index, list);
-        if (computed < lastComputed || computed === Infinity && result === Infinity) {
-          result = value;
-          lastComputed = computed;
-        }
-      });
+  _.min = function(obj, iterator, context) {
+    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
+      return Math.min.apply(Math, obj);
     }
+    var result = Infinity, lastComputed = Infinity;
+    each(obj, function(value, index, list) {
+      var computed = iterator ? iterator.call(context, value, index, list) : value;
+      if (computed < lastComputed) {
+        result = value;
+        lastComputed = computed;
+      }
+    });
     return result;
   };
 
-  // Shuffle a collection, using the modern version of the
+  // Shuffle an array, using the modern version of the
   // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
   _.shuffle = function(obj) {
-    var set = obj && obj.length === +obj.length ? obj : _.values(obj);
-    var length = set.length;
-    var shuffled = Array(length);
-    for (var index = 0, rand; index < length; index++) {
-      rand = _.random(0, index);
-      if (rand !== index) shuffled[index] = shuffled[rand];
-      shuffled[rand] = set[index];
-    }
+    var rand;
+    var index = 0;
+    var shuffled = [];
+    each(obj, function(value) {
+      rand = _.random(index++);
+      shuffled[index - 1] = shuffled[rand];
+      shuffled[rand] = value;
+    });
     return shuffled;
   };
 
@@ -387,28 +307,41 @@
     return _.shuffle(obj).slice(0, Math.max(0, n));
   };
 
-  // Sort the object's values by a criterion produced by an iteratee.
-  _.sortBy = function(obj, iteratee, context) {
-    iteratee = cb(iteratee, context);
+  // An internal function to generate lookup iterators.
+  var lookupIterator = function(value) {
+    if (value == null) return _.identity;
+    if (_.isFunction(value)) return value;
+    return _.property(value);
+  };
+
+  // Sort the object's values by a criterion produced by an iterator.
+  _.sortBy = function(obj, iterator, context) {
+    iterator = lookupIterator(iterator);
     return _.pluck(_.map(obj, function(value, index, list) {
       return {
         value: value,
         index: index,
-        criteria: iteratee(value, index, list)
+        criteria: iterator.call(context, value, index, list)
       };
     }).sort(function(left, right) {
-      return _.comparator(left.criteria, right.criteria) || left.index - right.index;
+      var a = left.criteria;
+      var b = right.criteria;
+      if (a !== b) {
+        if (a > b || a === void 0) return 1;
+        if (a < b || b === void 0) return -1;
+      }
+      return left.index - right.index;
     }), 'value');
   };
 
   // An internal function used for aggregate "group by" operations.
   var group = function(behavior) {
-    return function(obj, iteratee, context) {
+    return function(obj, iterator, context) {
       var result = {};
-      iteratee = cb(iteratee, context);
-      _.each(obj, function(value, index) {
-        var key = iteratee(value, index, obj);
-        behavior(result, value, key);
+      iterator = lookupIterator(iterator);
+      each(obj, function(value, index) {
+        var key = iterator.call(context, value, index, obj);
+        behavior(result, key, value);
       });
       return result;
     };
@@ -416,23 +349,36 @@
 
   // Groups the object's values by a criterion. Pass either a string attribute
   // to group by, or a function that returns the criterion.
-  _.groupBy = group(function(result, value, key) {
-    if (_.has(result, key)) result[key].push(value); else result[key] = [value];
+  _.groupBy = group(function(result, key, value) {
+    _.has(result, key) ? result[key].push(value) : result[key] = [value];
   });
 
   // Indexes the object's values by a criterion, similar to `groupBy`, but for
   // when you know that your index values will be unique.
-  _.indexBy = group(function(result, value, key) {
+  _.indexBy = group(function(result, key, value) {
     result[key] = value;
   });
 
   // Counts instances of an object that group by a certain criterion. Pass
   // either a string attribute to count by, or a function that returns the
   // criterion.
-  _.countBy = group(function(result, value, key) {
-    if (_.has(result, key)) result[key]++; else result[key] = 1;
+  _.countBy = group(function(result, key) {
+    _.has(result, key) ? result[key]++ : result[key] = 1;
   });
 
+  // Use a comparator function to figure out the smallest index at which
+  // an object should be inserted so as to maintain order. Uses binary search.
+  _.sortedIndex = function(array, obj, iterator, context) {
+    iterator = lookupIterator(iterator);
+    var value = iterator.call(context, obj);
+    var low = 0, high = array.length;
+    while (low < high) {
+      var mid = (low + high) >>> 1;
+      iterator.call(context, array[mid]) < value ? low = mid + 1 : high = mid;
+    }
+    return low;
+  };
+
   // Safely create a real, live array from anything iterable.
   _.toArray = function(obj) {
     if (!obj) return [];
@@ -444,18 +390,7 @@
   // Return the number of elements in an object.
   _.size = function(obj) {
     if (obj == null) return 0;
-    return obj.length === +obj.length ? obj.length : _.keys(obj).length;
-  };
-
-  // Split a collection into two arrays: one whose elements all satisfy the given
-  // predicate, and one whose elements all do not satisfy the predicate.
-  _.partition = function(obj, predicate, context) {
-    predicate = cb(predicate, context);
-    var pass = [], fail = [];
-    _.each(obj, function(value, key, obj) {
-      (predicate(value, key, obj) ? pass : fail).push(value);
-    });
-    return [pass, fail];
+    return (obj.length === +obj.length) ? obj.length : _.keys(obj).length;
   };
 
   // Array Functions
@@ -466,8 +401,9 @@
   // allows it to work with `_.map`.
   _.first = _.head = _.take = function(array, n, guard) {
     if (array == null) return void 0;
-    if (n == null || guard) return array[0];
-    return _.initial(array, array.length - n);
+    if ((n == null) || guard) return array[0];
+    if (n < 0) return [];
+    return slice.call(array, 0, n);
   };
 
   // Returns everything but the last entry of the array. Especially useful on
@@ -475,15 +411,15 @@
   // the array, excluding the last N. The **guard** check allows it to work with
   // `_.map`.
   _.initial = function(array, n, guard) {
-    return slice.call(array, 0, Math.max(0, array.length - (n == null || guard ? 1 : n)));
+    return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
   };
 
   // Get the last element of an array. Passing **n** will return the last N
   // values in the array. The **guard** check allows it to work with `_.map`.
   _.last = function(array, n, guard) {
     if (array == null) return void 0;
-    if (n == null || guard) return array[array.length - 1];
-    return _.rest(array, Math.max(0, array.length - n));
+    if ((n == null) || guard) return array[array.length - 1];
+    return slice.call(array, Math.max(array.length - n, 0));
   };
 
   // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
@@ -491,7 +427,7 @@
   // the rest N values in the array. The **guard**
   // check allows it to work with `_.map`.
   _.rest = _.tail = _.drop = function(array, n, guard) {
-    return slice.call(array, n == null || guard ? 1 : n);
+    return slice.call(array, (n == null) || guard ? 1 : n);
   };
 
   // Trim out all falsy values from an array.
@@ -500,28 +436,23 @@
   };
 
   // Internal implementation of a recursive `flatten` function.
-  var flatten = function(input, shallow, strict, startIndex) {
-    var output = [], idx = 0, value;
-    for (var i = startIndex || 0, length = input && input.length; i < length; i++) {
-      value = input[i];
-      if (value && value.length >= 0 && (_.isArray(value) || _.isArguments(value))) {
-        //flatten current level of array or arguments object
-        if (!shallow) value = flatten(value, shallow, strict);
-        var j = 0, len = value.length;
-        output.length += len;
-        while (j < len) {
-          output[idx++] = value[j++];
-        }
-      } else if (!strict) {
-        output[idx++] = value;
-      }
+  var flatten = function(input, shallow, output) {
+    if (shallow && _.every(input, _.isArray)) {
+      return concat.apply(output, input);
     }
+    each(input, function(value) {
+      if (_.isArray(value) || _.isArguments(value)) {
+        shallow ? push.apply(output, value) : flatten(value, shallow, output);
+      } else {
+        output.push(value);
+      }
+    });
     return output;
   };
 
   // Flatten out an array, either recursively (by default), or just one level.
   _.flatten = function(array, shallow) {
-    return flatten(array, shallow, false);
+    return flatten(array, shallow, []);
   };
 
   // Return a version of the array that does not contain the specified value(s).
@@ -529,87 +460,72 @@
     return _.difference(array, slice.call(arguments, 1));
   };
 
+  // Split an array into two arrays: one whose elements all satisfy the given
+  // predicate, and one whose elements all do not satisfy the predicate.
+  _.partition = function(array, predicate) {
+    var pass = [], fail = [];
+    each(array, function(elem) {
+      (predicate(elem) ? pass : fail).push(elem);
+    });
+    return [pass, fail];
+  };
+
   // Produce a duplicate-free version of the array. If the array has already
   // been sorted, you have the option of using a faster algorithm.
   // Aliased as `unique`.
-  _.uniq = _.unique = function(array, isSorted, iteratee, context) {
-    if (array == null) return [];
-    if (!_.isBoolean(isSorted)) {
-      context = iteratee;
-      iteratee = isSorted;
+  _.uniq = _.unique = function(array, isSorted, iterator, context) {
+    if (_.isFunction(isSorted)) {
+      context = iterator;
+      iterator = isSorted;
       isSorted = false;
     }
-    if (iteratee != null) iteratee = cb(iteratee, context);
-    var result = [];
+    var initial = iterator ? _.map(array, iterator, context) : array;
+    var results = [];
     var seen = [];
-    for (var i = 0, length = array.length; i < length; i++) {
-      var value = array[i],
-          computed = iteratee ? iteratee(value, i, array) : value;
-      if (isSorted) {
-        if (!i || seen !== computed) result.push(value);
-        seen = computed;
-      } else if (iteratee) {
-        if (!_.contains(seen, computed)) {
-          seen.push(computed);
-          result.push(value);
-        }
-      } else if (!_.contains(result, value)) {
-        result.push(value);
+    each(initial, function(value, index) {
+      if (isSorted ? (!index || seen[seen.length - 1] !== value) : !_.contains(seen, value)) {
+        seen.push(value);
+        results.push(array[index]);
       }
-    }
-    return result;
+    });
+    return results;
   };
 
   // Produce an array that contains the union: each distinct element from all of
   // the passed-in arrays.
   _.union = function() {
-    return _.uniq(flatten(arguments, true, true));
+    return _.uniq(_.flatten(arguments, true));
   };
 
   // Produce an array that contains every item shared between all the
   // passed-in arrays.
   _.intersection = function(array) {
-    if (array == null) return [];
-    var result = [];
-    var argsLength = arguments.length;
-    for (var i = 0, length = array.length; i < length; i++) {
-      var item = array[i];
-      if (_.contains(result, item)) continue;
-      for (var j = 1; j < argsLength; j++) {
-        if (!_.contains(arguments[j], item)) break;
-      }
-      if (j === argsLength) result.push(item);
-    }
-    return result;
+    var rest = slice.call(arguments, 1);
+    return _.filter(_.uniq(array), function(item) {
+      return _.every(rest, function(other) {
+        return _.contains(other, item);
+      });
+    });
   };
 
   // Take the difference between one array and a number of other arrays.
   // Only the elements present in just the first array will remain.
   _.difference = function(array) {
-    var rest = flatten(arguments, true, true, 1);
-    return _.filter(array, function(value){
-      return !_.contains(rest, value);
-    });
+    var rest = concat.apply(ArrayProto, slice.call(arguments, 1));
+    return _.filter(array, function(value){ return !_.contains(rest, value); });
   };
 
   // Zip together multiple lists into a single array -- elements that share
   // an index go together.
-  _.zip = function(array) {
-    if (array == null) return [];
-    var length = _.max(arguments, 'length').length;
-    var results = Array(length);
-    while (length-- > 0) {
-      results[length] = _.pluck(arguments, length);
+  _.zip = function() {
+    var length = _.max(_.pluck(arguments, 'length').concat(0));
+    var results = new Array(length);
+    for (var i = 0; i < length; i++) {
+      results[i] = _.pluck(arguments, '' + i);
     }
     return results;
   };
 
-  // Complement of _.zip. Unzip accepts an array of arrays and groups
-  // each array's elements on shared indices
-  _.unzip = function(array) {
-    return _.zip.apply(null, array);
-  };
-
   // Converts lists into objects. Pass either a single array of `[key, value]`
   // pairs, or two parallel arrays of the same length -- one of keys, and one of
   // the corresponding values.
@@ -626,54 +542,40 @@
     return result;
   };
 
-  // Return the position of the first occurrence of an item in an array,
-  // or -1 if the item is not included in the array.
+  // If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
+  // we need this function. Return the position of the first occurrence of an
+  // item in an array, or -1 if the item is not included in the array.
+  // Delegates to **ECMAScript 5**'s native `indexOf` if available.
   // If the array is large and already in sort order, pass `true`
   // for **isSorted** to use binary search.
   _.indexOf = function(array, item, isSorted) {
-    var i = 0, length = array && array.length;
-    if (typeof isSorted == 'number') {
-      i = isSorted < 0 ? Math.max(0, length + isSorted) : isSorted;
-    } else if (isSorted && length) {
-      i = _.sortedIndex(array, item);
-      return array[i] === item ? i : -1;
+    if (array == null) return -1;
+    var i = 0, length = array.length;
+    if (isSorted) {
+      if (typeof isSorted == 'number') {
+        i = (isSorted < 0 ? Math.max(0, length + isSorted) : isSorted);
+      } else {
+        i = _.sortedIndex(array, item);
+        return array[i] === item ? i : -1;
+      }
     }
+    if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item, isSorted);
     for (; i < length; i++) if (array[i] === item) return i;
     return -1;
   };
 
+  // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
   _.lastIndexOf = function(array, item, from) {
-    var idx = array ? array.length : 0;
-    if (typeof from == 'number') {
-      idx = from < 0 ? idx + from + 1 : Math.min(idx, from + 1);
+    if (array == null) return -1;
+    var hasIndex = from != null;
+    if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) {
+      return hasIndex ? array.lastIndexOf(item, from) : array.lastIndexOf(item);
     }
-    while (--idx >= 0) if (array[idx] === item) return idx;
+    var i = (hasIndex ? from : array.length);
+    while (i--) if (array[i] === item) return i;
     return -1;
   };
 
-  // Returns the first index on an array-like that passes a predicate test
-  _.findIndex = function(array, predicate, context) {
-    predicate = cb(predicate, context);
-    var length = array != null ? array.length : 0;
-    for (var i = 0; i < length; i++) {
-      if (predicate(array[i], i, array)) return i;
-    }
-    return -1;
-  };
-
-  // Use a comparator function to figure out the smallest index at which
-  // an object should be inserted so as to maintain order. Uses binary search.
-  _.sortedIndex = function(array, obj, iteratee, context) {
-    iteratee = cb(iteratee, context, 1);
-    var value = iteratee(obj);
-    var low = 0, high = array.length;
-    while (low < high) {
-      var mid = Math.floor((low + high) / 2);
-      if (_.comparator(iteratee(array[mid]), value) < 0) low = mid + 1; else high = mid;
-    }
-    return low;
-  };
-
   // Generate an integer Array containing an arithmetic progression. A port of
   // the native Python `range()` function. See
   // [the Python documentation](http://docs.python.org/library/functions.html#range).
@@ -682,13 +584,15 @@
       stop = start || 0;
       start = 0;
     }
-    step = step || 1;
+    step = arguments[2] || 1;
 
     var length = Math.max(Math.ceil((stop - start) / step), 0);
-    var range = Array(length);
+    var idx = 0;
+    var range = new Array(length);
 
-    for (var idx = 0; idx < length; idx++, start += step) {
-      range[idx] = start;
+    while(idx < length) {
+      range[idx++] = start;
+      start += step;
     }
 
     return range;
@@ -697,25 +601,25 @@
   // Function (ahem) Functions
   // ------------------
 
-  // Determines whether to execute a function as a constructor
-  // or a normal function with the provided arguments
-  var executeBound = function(sourceFunc, boundFunc, context, callingContext, args) {
-    if (!(callingContext instanceof boundFunc)) return sourceFunc.apply(context, args);
-    var self = baseCreate(sourceFunc.prototype);
-    var result = sourceFunc.apply(self, args);
-    if (_.isObject(result)) return result;
-    return self;
-  };
+  // Reusable constructor function for prototype setting.
+  var ctor = function(){};
 
   // Create a function bound to a given object (assigning `this`, and arguments,
   // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
   // available.
   _.bind = function(func, context) {
+    var args, bound;
     if (nativeBind && func.bind === nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
-    if (!_.isFunction(func)) throw new TypeError('Bind must be called on a function');
-    var args = slice.call(arguments, 2);
-    return function bound() {
-      return executeBound(func, bound, context, this, args.concat(slice.call(arguments)));
+    if (!_.isFunction(func)) throw new TypeError;
+    args = slice.call(arguments, 2);
+    return bound = function() {
+      if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
+      ctor.prototype = func.prototype;
+      var self = new ctor;
+      ctor.prototype = null;
+      var result = func.apply(self, args.concat(slice.call(arguments)));
+      if (Object(result) === result) return result;
+      return self;
     };
   };
 
@@ -724,14 +628,14 @@
   // as a placeholder, allowing any combination of arguments to be pre-filled.
   _.partial = function(func) {
     var boundArgs = slice.call(arguments, 1);
-    return function bound() {
+    return function() {
       var position = 0;
       var args = boundArgs.slice();
       for (var i = 0, length = args.length; i < length; i++) {
         if (args[i] === _) args[i] = arguments[position++];
       }
       while (position < arguments.length) args.push(arguments[position++]);
-      return executeBound(func, bound, this, this, args);
+      return func.apply(this, args);
     };
   };
 
@@ -739,39 +643,34 @@
   // are the method names to be bound. Useful for ensuring that all callbacks
   // defined on an object belong to it.
   _.bindAll = function(obj) {
-    var i, length = arguments.length, key;
-    if (length <= 1) throw new Error('bindAll must be passed function names');
-    for (i = 1; i < length; i++) {
-      key = arguments[i];
-      obj[key] = _.bind(obj[key], obj);
-    }
+    var funcs = slice.call(arguments, 1);
+    if (funcs.length === 0) throw new Error('bindAll must be passed function names');
+    each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
     return obj;
   };
 
   // Memoize an expensive function by storing its results.
   _.memoize = function(func, hasher) {
-    var memoize = function(key) {
-      var cache = memoize.cache;
-      var address = '' + (hasher ? hasher.apply(this, arguments) : key);
-      if (!_.has(cache, address)) cache[address] = func.apply(this, arguments);
-      return cache[address];
+    var memo = {};
+    hasher || (hasher = _.identity);
+    return function() {
+      var key = hasher.apply(this, arguments);
+      return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
     };
-    memoize.cache = {};
-    return memoize;
   };
 
   // Delays a function for the given number of milliseconds, and then calls
   // it with the arguments supplied.
   _.delay = function(func, wait) {
     var args = slice.call(arguments, 2);
-    return setTimeout(function(){
-      return func.apply(null, args);
-    }, wait);
+    return setTimeout(function(){ return func.apply(null, args); }, wait);
   };
 
   // Defers a function, scheduling it to run after the current call stack has
   // cleared.
-  _.defer = _.partial(_.delay, _, 1);
+  _.defer = function(func) {
+    return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
+  };
 
   // Returns a function, that, when invoked, will only be triggered at most once
   // during a given window of time. Normally, the throttled function will run
@@ -782,12 +681,12 @@
     var context, args, result;
     var timeout = null;
     var previous = 0;
-    if (!options) options = {};
+    options || (options = {});
     var later = function() {
       previous = options.leading === false ? 0 : _.now();
       timeout = null;
       result = func.apply(context, args);
-      if (!timeout) context = args = null;
+      context = args = null;
     };
     return function() {
       var now = _.now();
@@ -795,14 +694,12 @@
       var remaining = wait - (now - previous);
       context = this;
       args = arguments;
-      if (remaining <= 0 || remaining > wait) {
-        if (timeout) {
-          clearTimeout(timeout);
-          timeout = null;
-        }
+      if (remaining <= 0) {
+        clearTimeout(timeout);
+        timeout = null;
         previous = now;
         result = func.apply(context, args);
-        if (!timeout) context = args = null;
+        context = args = null;
       } else if (!timeout && options.trailing !== false) {
         timeout = setTimeout(later, remaining);
       }
@@ -819,14 +716,13 @@
 
     var later = function() {
       var last = _.now() - timestamp;
-
-      if (last < wait && last >= 0) {
+      if (last < wait) {
         timeout = setTimeout(later, wait - last);
       } else {
         timeout = null;
         if (!immediate) {
           result = func.apply(context, args);
-          if (!timeout) context = args = null;
+          context = args = null;
         }
       }
     };
@@ -836,7 +732,9 @@
       args = arguments;
       timestamp = _.now();
       var callNow = immediate && !timeout;
-      if (!timeout) timeout = setTimeout(later, wait);
+      if (!timeout) {
+        timeout = setTimeout(later, wait);
+      }
       if (callNow) {
         result = func.apply(context, args);
         context = args = null;
@@ -846,6 +744,19 @@
     };
   };
 
+  // Returns a function that will be executed at most one time, no matter how
+  // often you call it. Useful for lazy initialization.
+  _.once = function(func) {
+    var ran = false, memo;
+    return function() {
+      if (ran) return memo;
+      ran = true;
+      memo = func.apply(this, arguments);
+      func = null;
+      return memo;
+    };
+  };
+
   // Returns the first function passed as an argument to the second,
   // allowing you to adjust arguments, run code before and after, and
   // conditionally execute the original function.
@@ -853,27 +764,20 @@
     return _.partial(wrapper, func);
   };
 
-  // Returns a negated version of the passed-in predicate.
-  _.negate = function(predicate) {
-    return function() {
-      return !predicate.apply(this, arguments);
-    };
-  };
-
   // Returns a function that is the composition of a list of functions, each
   // consuming the return value of the function that follows.
   _.compose = function() {
-    var args = arguments;
-    var start = args.length - 1;
+    var funcs = arguments;
     return function() {
-      var i = start;
-      var result = args[start].apply(this, arguments);
-      while (i--) result = args[i].call(this, result);
-      return result;
+      var args = arguments;
+      for (var i = funcs.length - 1; i >= 0; i--) {
+        args = [funcs[i].apply(this, args)];
+      }
+      return args[0];
     };
   };
 
-  // Returns a function that will only be executed on and after the Nth call.
+  // Returns a function that will only be executed after being called N times.
   _.after = function(times, func) {
     return function() {
       if (--times < 1) {
@@ -882,62 +786,16 @@
     };
   };
 
-  // Returns a function that will only be executed up to (but not including) the Nth call.
-  _.before = function(times, func) {
-    var memo;
-    return function() {
-      if (--times > 0) {
-        memo = func.apply(this, arguments);
-      }
-      if (times <= 1) func = null;
-      return memo;
-    };
-  };
-
-  // Returns a function that will be executed at most one time, no matter how
-  // often you call it. Useful for lazy initialization.
-  _.once = _.partial(_.before, 2);
-
   // Object Functions
   // ----------------
 
-  // Keys in IE < 9 that won't be iterated by `for key in ...` and thus missed.
-  var hasEnumBug = !{toString: null}.propertyIsEnumerable('toString');
-  var nonEnumerableProps = ['constructor', 'valueOf', 'isPrototypeOf', 'toString',
-                      'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];
-
-  function collectNonEnumProps(obj, keys) {
-    var nonEnumIdx = nonEnumerableProps.length;
-    var proto = typeof obj.constructor === 'function' ? FuncProto : ObjProto;
-
-    while (nonEnumIdx--) {
-      var prop = nonEnumerableProps[nonEnumIdx];
-      if (prop === 'constructor' ? _.has(obj, prop) : prop in obj &&
-        obj[prop] !== proto[prop] && !_.contains(keys, prop)) {
-        keys.push(prop);
-      }
-    }
-  }
-
-  // Retrieve the names of an object's own properties.
+  // Retrieve the names of an object's properties.
   // Delegates to **ECMAScript 5**'s native `Object.keys`
   _.keys = function(obj) {
     if (!_.isObject(obj)) return [];
     if (nativeKeys) return nativeKeys(obj);
     var keys = [];
     for (var key in obj) if (_.has(obj, key)) keys.push(key);
-    // Ahem, IE < 9.
-    if (hasEnumBug) collectNonEnumProps(obj, keys);
-    return keys;
-  };
-
-  // Retrieve all the property names of an object.
-  _.keysIn = function(obj) {
-    if (!_.isObject(obj)) return [];
-    var keys = [];
-    for (var key in obj) keys.push(key);
-    // Ahem, IE < 9.
-    if (hasEnumBug) collectNonEnumProps(obj, keys);
     return keys;
   };
 
@@ -945,7 +803,7 @@
   _.values = function(obj) {
     var keys = _.keys(obj);
     var length = keys.length;
-    var values = Array(length);
+    var values = new Array(length);
     for (var i = 0; i < length; i++) {
       values[i] = obj[keys[i]];
     }
@@ -956,7 +814,7 @@
   _.pairs = function(obj) {
     var keys = _.keys(obj);
     var length = keys.length;
-    var pairs = Array(length);
+    var pairs = new Array(length);
     for (var i = 0; i < length; i++) {
       pairs[i] = [keys[i], obj[keys[i]]];
     }
@@ -984,77 +842,49 @@
   };
 
   // Extend a given object with all the properties in passed-in object(s).
-  _.extend = createAssigner(_.keysIn);
-
-  // Assigns a given object with all the own properties in the passed-in object(s)
-  // (https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign)
-  _.assign = createAssigner(_.keys);
-
-  // Returns the first key on an object that passes a predicate test
-  _.findKey = function(obj, predicate, context) {
-    predicate = cb(predicate, context);
-    var keys = _.keys(obj), key;
-    for (var i = 0, length = keys.length; i < length; i++) {
-      key = keys[i];
-      if (predicate(obj[key], key, obj)) return key;
-    }
+  _.extend = function(obj) {
+    each(slice.call(arguments, 1), function(source) {
+      if (source) {
+        for (var prop in source) {
+          obj[prop] = source[prop];
+        }
+      }
+    });
+    return obj;
   };
 
   // Return a copy of the object only containing the whitelisted properties.
-  _.pick = function(obj, iteratee, context) {
-    var result = {}, key;
-    if (obj == null) return result;
-    if (_.isFunction(iteratee)) {
-      iteratee = optimizeCb(iteratee, context);
-      for (key in obj) {
-        var value = obj[key];
-        if (iteratee(value, key, obj)) result[key] = value;
-      }
-    } else {
-      var keys = flatten(arguments, false, false, 1);
-      obj = new Object(obj);
-      for (var i = 0, length = keys.length; i < length; i++) {
-        key = keys[i];
-        if (key in obj) result[key] = obj[key];
-      }
-    }
-    return result;
+  _.pick = function(obj) {
+    var copy = {};
+    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
+    each(keys, function(key) {
+      if (key in obj) copy[key] = obj[key];
+    });
+    return copy;
   };
 
    // Return a copy of the object without the blacklisted properties.
-  _.omit = function(obj, iteratee, context) {
-    if (_.isFunction(iteratee)) {
-      iteratee = _.negate(iteratee);
-    } else {
-      var keys = _.map(flatten(arguments, false, false, 1), String);
-      iteratee = function(value, key) {
-        return !_.contains(keys, key);
-      };
+  _.omit = function(obj) {
+    var copy = {};
+    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
+    for (var key in obj) {
+      if (!_.contains(keys, key)) copy[key] = obj[key];
     }
-    return _.pick(obj, iteratee, context);
+    return copy;
   };
 
   // Fill in a given object with default properties.
   _.defaults = function(obj) {
-    if (!_.isObject(obj)) return obj;
-    for (var i = 1, length = arguments.length; i < length; i++) {
-      var source = arguments[i];
-      for (var prop in source) {
-        if (obj[prop] === void 0) obj[prop] = source[prop];
+    each(slice.call(arguments, 1), function(source) {
+      if (source) {
+        for (var prop in source) {
+          if (obj[prop] === void 0) obj[prop] = source[prop];
+        }
       }
-    }
+    });
     return obj;
   };
 
-  // Creates an object that inherits from the given prototype object.
-  // If additional properties are provided then they will be added to the
-  // created object.
-  _.create = function(prototype, props) {
-    var result = baseCreate(prototype);
-    if (props) _.assign(result, props);
-    return result;
-  };
-
   // Create a (shallow-cloned) duplicate of an object.
   _.clone = function(obj) {
     if (!_.isObject(obj)) return obj;
@@ -1073,7 +903,7 @@
   var eq = function(a, b, aStack, bStack) {
     // Identical objects are equal. `0 === -0`, but they aren't identical.
     // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
-    if (a === b) return a !== 0 || 1 / a === 1 / b;
+    if (a === b) return a !== 0 || 1 / a == 1 / b;
     // A strict comparison is necessary because `null == undefined`.
     if (a == null || b == null) return a === b;
     // Unwrap any wrapped objects.
@@ -1081,80 +911,84 @@
     if (b instanceof _) b = b._wrapped;
     // Compare `[[Class]]` names.
     var className = toString.call(a);
-    if (className !== toString.call(b)) return false;
+    if (className != toString.call(b)) return false;
     switch (className) {
-      // Strings, numbers, regular expressions, dates, and booleans are compared by value.
-      case '[object RegExp]':
-      // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
+      // Strings, numbers, dates, and booleans are compared by value.
       case '[object String]':
         // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
         // equivalent to `new String("5")`.
-        return '' + a === '' + b;
+        return a == String(b);
       case '[object Number]':
-        // `NaN`s are equivalent, but non-reflexive.
-        // Object(NaN) is equivalent to NaN
-        if (+a !== +a) return +b !== +b;
-        // An `egal` comparison is performed for other numeric values.
-        return +a === 0 ? 1 / +a === 1 / b : +a === +b;
+        // `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
+        // other numeric values.
+        return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
       case '[object Date]':
       case '[object Boolean]':
         // Coerce dates and booleans to numeric primitive values. Dates are compared by their
         // millisecond representations. Note that invalid dates with millisecond representations
         // of `NaN` are not equivalent.
-        return +a === +b;
-    }
-
-    var areArrays = className === '[object Array]';
-    if (!areArrays) {
-      if (typeof a != 'object' || typeof b != 'object') return false;
-
-      // Objects with different constructors are not equivalent, but `Object`s or `Array`s
-      // from different frames are.
-      var aCtor = a.constructor, bCtor = b.constructor;
-      if (aCtor !== bCtor && !(_.isFunction(aCtor) && aCtor instanceof aCtor &&
-                               _.isFunction(bCtor) && bCtor instanceof bCtor)
-                          && ('constructor' in a && 'constructor' in b)) {
-        return false;
-      }
+        return +a == +b;
+      // RegExps are compared by their source patterns and flags.
+      case '[object RegExp]':
+        return a.source == b.source &&
+               a.global == b.global &&
+               a.multiline == b.multiline &&
+               a.ignoreCase == b.ignoreCase;
     }
+    if (typeof a != 'object' || typeof b != 'object') return false;
     // Assume equality for cyclic structures. The algorithm for detecting cyclic
     // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
     var length = aStack.length;
     while (length--) {
       // Linear search. Performance is inversely proportional to the number of
       // unique nested structures.
-      if (aStack[length] === a) return bStack[length] === b;
+      if (aStack[length] == a) return bStack[length] == b;
+    }
+    // Objects with different constructors are not equivalent, but `Object`s
+    // from different frames are.
+    var aCtor = a.constructor, bCtor = b.constructor;
+    if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
+                             _.isFunction(bCtor) && (bCtor instanceof bCtor))
+                        && ('constructor' in a && 'constructor' in b)) {
+      return false;
     }
-
     // Add the first object to the stack of traversed objects.
     aStack.push(a);
     bStack.push(b);
-
+    var size = 0, result = true;
     // Recursively compare objects and arrays.
-    if (areArrays) {
+    if (className == '[object Array]') {
       // Compare array lengths to determine if a deep comparison is necessary.
-      length = a.length;
-      if (length !== b.length) return false;
-      // Deep compare the contents, ignoring non-numeric properties.
-      while (length--) {
-        if (!eq(a[length], b[length], aStack, bStack)) return false;
+      size = a.length;
+      result = size == b.length;
+      if (result) {
+        // Deep compare the contents, ignoring non-numeric properties.
+        while (size--) {
+          if (!(result = eq(a[size], b[size], aStack, bStack))) break;
+        }
       }
     } else {
       // Deep compare objects.
-      var keys = _.keys(a), key;
-      length = keys.length;
-      // Ensure that both objects contain the same number of properties before comparing deep equality.
-      if (_.keys(b).length !== length) return false;
-      while (length--) {
-        // Deep compare each member
-        key = keys[length];
-        if (!(_.has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
+      for (var key in a) {
+        if (_.has(a, key)) {
+          // Count the expected number of properties.
+          size++;
+          // Deep compare each member.
+          if (!(result = _.has(b, key) && eq(a[key], b[key], aStack, bStack))) break;
+        }
+      }
+      // Ensure that both objects contain the same number of properties.
+      if (result) {
+        for (key in b) {
+          if (_.has(b, key) && !(size--)) break;
+        }
+        result = !size;
       }
     }
     // Remove the first object from the stack of traversed objects.
     aStack.pop();
     bStack.pop();
-    return true;
+    return result;
   };
 
   // Perform a deep comparison to check if two objects are equal.
@@ -1166,7 +1000,7 @@
   // An "empty" object has no enumerable own-properties.
   _.isEmpty = function(obj) {
     if (obj == null) return true;
-    if (_.isArray(obj) || _.isString(obj) || _.isArguments(obj)) return obj.length === 0;
+    if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
     for (var key in obj) if (_.has(obj, key)) return false;
     return true;
   };
@@ -1179,35 +1013,33 @@
   // Is a given value an array?
   // Delegates to ECMA5's native Array.isArray
   _.isArray = nativeIsArray || function(obj) {
-    return toString.call(obj) === '[object Array]';
+    return toString.call(obj) == '[object Array]';
   };
 
   // Is a given variable an object?
   _.isObject = function(obj) {
-    var type = typeof obj;
-    return type === 'function' || type === 'object' && !!obj;
+    return obj === Object(obj);
   };
 
-  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
-  _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
+  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.
+  each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) {
     _['is' + name] = function(obj) {
-      return toString.call(obj) === '[object ' + name + ']';
+      return toString.call(obj) == '[object ' + name + ']';
     };
   });
 
-  // Define a fallback version of the method in browsers (ahem, IE < 9), where
+  // Define a fallback version of the method in browsers (ahem, IE), where
   // there isn't any inspectable "Arguments" type.
   if (!_.isArguments(arguments)) {
     _.isArguments = function(obj) {
-      return _.has(obj, 'callee');
+      return !!(obj && _.has(obj, 'callee'));
     };
   }
 
-  // Optimize `isFunction` if appropriate. Work around an IE 11 bug (#1621).
-  // Work around a Safari 8 bug (#1929)
-  if (typeof /./ != 'function' && typeof Int8Array != 'object') {
+  // Optimize `isFunction` if appropriate.
+  if (typeof (/./) !== 'function') {
     _.isFunction = function(obj) {
-      return typeof obj == 'function' || false;
+      return typeof obj === 'function';
     };
   }
 
@@ -1218,12 +1050,12 @@
 
   // Is the given value `NaN`? (NaN is the only number which does not equal itself).
   _.isNaN = function(obj) {
-    return _.isNumber(obj) && obj !== +obj;
+    return _.isNumber(obj) && obj != +obj;
   };
 
   // Is a given value a boolean?
   _.isBoolean = function(obj) {
-    return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
+    return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
   };
 
   // Is a given value equal to null?
@@ -1239,7 +1071,7 @@
   // Shortcut function for checking if an object has a given property directly
   // on itself (in other words, not on a prototype).
   _.has = function(obj, key) {
-    return obj != null && hasOwnProperty.call(obj, key);
+    return hasOwnProperty.call(obj, key);
   };
 
   // Utility Functions
@@ -1252,64 +1084,39 @@
     return this;
   };
 
-  // Keep the identity function around for default iteratees.
+  // Keep the identity function around for default iterators.
   _.identity = function(value) {
     return value;
   };
 
-  // Predicate-generating functions. Often useful outside of Underscore.
   _.constant = function(value) {
-    return function() {
+    return function () {
       return value;
     };
   };
 
-  _.noop = function(){};
-
   _.property = function(key) {
     return function(obj) {
-      return obj == null ? void 0 : obj[key];
-    };
-  };
-
-  // Generates a function for a given object that returns a given property (including those of ancestors)
-  _.propertyOf = function(obj) {
-    return obj == null ? function(){} : function(key) {
       return obj[key];
     };
   };
 
   // Returns a predicate for checking whether an object has a given set of `key:value` pairs.
   _.matches = function(attrs) {
-    var pairs = _.pairs(attrs), length = pairs.length;
     return function(obj) {
-      if (obj == null) return !length;
-      obj = new Object(obj);
-      for (var i = 0; i < length; i++) {
-        var pair = pairs[i], key = pair[0];
-        if (pair[1] !== obj[key] || !(key in obj)) return false;
+      if (obj === attrs) return true; //avoid comparing an object to itself.
+      for (var key in attrs) {
+        if (attrs[key] !== obj[key])
+          return false;
       }
       return true;
-    };
-  };
-
-  // Default internal comparator for determining whether a is greater (1),
-  // equal (0) or less than (-1) some object b
-  _.comparator = function(a, b) {
-    if (a === b) return 0;
-    var isAComparable = a >= a, isBComparable = b >= b;
-    if (isAComparable || isBComparable) {
-      if (isAComparable && !isBComparable) return -1;
-      if (isBComparable && !isAComparable) return 1;
     }
-    return a > b ? 1 : (b > a) ? -1 : 0;
   };
 
   // Run a function **n** times.
-  _.times = function(n, iteratee, context) {
+  _.times = function(n, iterator, context) {
     var accum = Array(Math.max(0, n));
-    iteratee = optimizeCb(iteratee, context, 1);
-    for (var i = 0; i < n; i++) accum[i] = iteratee(i);
+    for (var i = 0; i < n; i++) accum[i] = iterator.call(context, i);
     return accum;
   };
 
@@ -1323,48 +1130,56 @@
   };
 
   // A (possibly faster) way to get the current timestamp as an integer.
-  _.now = Date.now || function() {
-    return new Date().getTime();
+  _.now = Date.now || function() { return new Date().getTime(); };
+
+  // List of HTML entities for escaping.
+  var entityMap = {
+    escape: {
+      '&': '&amp;',
+      '<': '&lt;',
+      '>': '&gt;',
+      '"': '&quot;',
+      "'": '&#x27;'
+    }
   };
+  entityMap.unescape = _.invert(entityMap.escape);
 
-   // List of HTML entities for escaping.
-  var escapeMap = {
-    '&': '&amp;',
-    '<': '&lt;',
-    '>': '&gt;',
-    '"': '&quot;',
-    "'": '&#x27;',
-    '`': '&#x60;'
+  // Regexes containing the keys and values listed immediately above.
+  var entityRegexes = {
+    escape:   new RegExp('[' + _.keys(entityMap.escape).join('') + ']', 'g'),
+    unescape: new RegExp('(' + _.keys(entityMap.unescape).join('|') + ')', 'g')
   };
-  var unescapeMap = _.invert(escapeMap);
 
   // Functions for escaping and unescaping strings to/from HTML interpolation.
-  var createEscaper = function(map) {
-    var escaper = function(match) {
-      return map[match];
-    };
-    // Regexes for identifying a key that needs to be escaped
-    var source = '(?:' + _.keys(map).join('|') + ')';
-    var testRegexp = RegExp(source);
-    var replaceRegexp = RegExp(source, 'g');
-    return function(string) {
-      string = string == null ? '' : '' + string;
-      return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
+  _.each(['escape', 'unescape'], function(method) {
+    _[method] = function(string) {
+      if (string == null) return '';
+      return ('' + string).replace(entityRegexes[method], function(match) {
+        return entityMap[method][match];
+      });
     };
-  };
-  _.escape = createEscaper(escapeMap);
-  _.unescape = createEscaper(unescapeMap);
+  });
 
   // If the value of the named `property` is a function then invoke it with the
   // `object` as context; otherwise, return it.
-  _.result = function(object, property, fallback) {
-    var value = object == null ? void 0 : object[property];
-    if (value === void 0) {
-      value = fallback;
-    }
+  _.result = function(object, property) {
+    if (object == null) return void 0;
+    var value = object[property];
     return _.isFunction(value) ? value.call(object) : value;
   };
 
+  // Add your own custom functions to the Underscore object.
+  _.mixin = function(obj) {
+    each(_.functions(obj), function(name) {
+      var func = _[name] = obj[name];
+      _.prototype[name] = function() {
+        var args = [this._wrapped];
+        push.apply(args, arguments);
+        return result.call(this, func.apply(_, args));
+      };
+    });
+  };
+
   // Generate a unique integer id (unique within the entire client session).
   // Useful for temporary DOM ids.
   var idCounter = 0;
@@ -1393,26 +1208,22 @@
     '\\':     '\\',
     '\r':     'r',
     '\n':     'n',
+    '\t':     't',
     '\u2028': 'u2028',
     '\u2029': 'u2029'
   };
 
-  var escaper = /\\|'|\r|\n|\u2028|\u2029/g;
-
-  var escapeChar = function(match) {
-    return '\\' + escapes[match];
-  };
+  var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
 
   // JavaScript micro-templating, similar to John Resig's implementation.
   // Underscore templating handles arbitrary delimiters, preserves whitespace,
   // and correctly escapes quotes within interpolated code.
-  // NB: `oldSettings` only exists for backwards compatibility.
-  _.template = function(text, settings, oldSettings) {
-    if (!settings && oldSettings) settings = oldSettings;
+  _.template = function(text, data, settings) {
+    var render;
     settings = _.defaults({}, settings, _.templateSettings);
 
     // Combine delimiters into one regular expression via alternation.
-    var matcher = RegExp([
+    var matcher = new RegExp([
       (settings.escape || noMatch).source,
       (settings.interpolate || noMatch).source,
       (settings.evaluate || noMatch).source
@@ -1422,18 +1233,19 @@
     var index = 0;
     var source = "__p+='";
     text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
-      source += text.slice(index, offset).replace(escaper, escapeChar);
-      index = offset + match.length;
+      source += text.slice(index, offset)
+        .replace(escaper, function(match) { return '\\' + escapes[match]; });
 
       if (escape) {
         source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
-      } else if (interpolate) {
+      }
+      if (interpolate) {
         source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
-      } else if (evaluate) {
+      }
+      if (evaluate) {
         source += "';\n" + evaluate + "\n__p+='";
       }
-
-      // Adobe VMs need the match returned to produce the correct offest.
+      index = offset + match.length;
       return match;
     });
     source += "';\n";
@@ -1443,31 +1255,29 @@
 
     source = "var __t,__p='',__j=Array.prototype.join," +
       "print=function(){__p+=__j.call(arguments,'');};\n" +
-      source + 'return __p;\n';
+      source + "return __p;\n";
 
     try {
-      var render = new Function(settings.variable || 'obj', '_', source);
+      render = new Function(settings.variable || 'obj', '_', source);
     } catch (e) {
       e.source = source;
       throw e;
     }
 
+    if (data) return render(data, _);
     var template = function(data) {
       return render.call(this, data, _);
     };
 
-    // Provide the compiled source as a convenience for precompilation.
-    var argument = settings.variable || 'obj';
-    template.source = 'function(' + argument + '){\n' + source + '}';
+    // Provide the compiled function source as a convenience for precompilation.
+    template.source = 'function(' + (settings.variable || 'obj') + '){\n' + source + '}';
 
     return template;
   };
 
-  // Add a "chain" function. Start chaining a wrapped Underscore object.
+  // Add a "chain" function, which will delegate to the wrapper.
   _.chain = function(obj) {
-    var instance = _(obj);
-    instance._chain = true;
-    return instance;
+    return _(obj).chain();
   };
 
   // OOP
@@ -1477,48 +1287,46 @@
   // underscore functions. Wrapped objects may be chained.
 
   // Helper function to continue chaining intermediate results.
-  var result = function(instance, obj) {
-    return instance._chain ? _(obj).chain() : obj;
-  };
-
-  // Add your own custom functions to the Underscore object.
-  _.mixin = function(obj) {
-    _.each(_.functions(obj), function(name) {
-      var func = _[name] = obj[name];
-      _.prototype[name] = function() {
-        var args = [this._wrapped];
-        push.apply(args, arguments);
-        return result(this, func.apply(_, args));
-      };
-    });
+  var result = function(obj) {
+    return this._chain ? _(obj).chain() : obj;
   };
 
   // Add all of the Underscore functions to the wrapper object.
   _.mixin(_);
 
   // Add all mutator Array functions to the wrapper.
-  _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
+  each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
     var method = ArrayProto[name];
     _.prototype[name] = function() {
       var obj = this._wrapped;
       method.apply(obj, arguments);
-      if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
-      return result(this, obj);
+      if ((name == 'shift' || name == 'splice') && obj.length === 0) delete obj[0];
+      return result.call(this, obj);
     };
   });
 
   // Add all accessor Array functions to the wrapper.
-  _.each(['concat', 'join', 'slice'], function(name) {
+  each(['concat', 'join', 'slice'], function(name) {
     var method = ArrayProto[name];
     _.prototype[name] = function() {
-      return result(this, method.apply(this._wrapped, arguments));
+      return result.call(this, method.apply(this._wrapped, arguments));
     };
   });
 
-  // Extracts the result from a wrapped and chained object.
-  _.prototype.value = function() {
-    return this._wrapped;
-  };
+  _.extend(_.prototype, {
+
+    // Start chaining a wrapped Underscore object.
+    chain: function() {
+      this._chain = true;
+      return this;
+    },
+
+    // Extracts the result from a wrapped and chained object.
+    value: function() {
+      return this._wrapped;
+    }
+
+  });
 
   // AMD registration happens at the end for compatibility with AMD loaders
   // that may not enforce next-turn semantics on modules. Even though general
@@ -1532,4 +1340,4 @@
       return _;
     });
   }
-}.call(this));
\ No newline at end of file
+}).call(this);
\ No newline at end of file

From 7c618edb3c1abda946eb67fc457b409f03c1cb8e Mon Sep 17 00:00:00 2001
From: Josh Bambrick <jpbambrick@gmail.com>
Date: Thu, 23 Apr 2015 19:40:50 +0100
Subject: [PATCH 11/11] add new line to underscore.js

to avoid having to update this file at all, adding the newline back in at the end
---
 test/vendor/underscore.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/vendor/underscore.js b/test/vendor/underscore.js
index 00d3deb92..9a4cabecf 100644
--- a/test/vendor/underscore.js
+++ b/test/vendor/underscore.js
@@ -1340,4 +1340,4 @@
       return _;
     });
   }
-}).call(this);
\ No newline at end of file
+}).call(this);