Worker.md

Worker

Namespace: SpawnDev.SpawnJS.JSObjects
Inherits: EventTarget, IMessagePort
Source: JSObjects/Worker.cs
MDN Reference: Worker on MDN

The Worker interface of the Web Workers API represents a background task that can be created via script, which can send messages back to its creator. https://developer.mozilla.org/en-US/docs/Web/API/Worker

Constructors

Signature	Description
Worker(SpawnJSObjectReference _ref)	Deserialization constructor
Worker(string url)	Creates a dedicated web worker that executes the script at the specified URL. This also works for Blob URLs. A string representing the URL of the script the worker will execute. It must obey the same-origin policy. The URL is resolved relative to the current HTML page's location.
Worker(string url, WorkerOptions options)	Creates a dedicated web worker that executes the script at the specified URL. This also works for Blob URLs. A string representing the URL of the script the worker will execute. It must obey the same-origin policy. The URL is resolved relative to the current HTML page's location. An object containing option properties that can be set when creating the Worker instance.

Methods

Method	Return Type	Description
Terminate()	void	Immediately terminates the worker. This does not let worker finish its operations; it is halted at once. ServiceWorker instances do not support this method.
PostMessage(object message)	void	Sends a message - consisting of any JavaScript object - to the worker's inner scope.
PostMessage(object message, object[] transfer)	void	Sends a message - consisting of any JavaScript object - to the worker's inner scope.

Events

Event	Type	Description
OnError	ActionEvent<Event>	Fires when an error occurs in the worker.
OnMessage	ActionEvent<MessageEvent>	Fires when the worker's parent receives a message from that worker.
OnMessageError	ActionEvent<MessageEvent>	Fires when a Worker object receives a message that can't be deserialized.

Example

// Create a dedicated web worker from a script URL
using var worker = new Worker("/js/my-worker.js");

// Listen for messages from the worker
Action<MessageEvent> onMessage = (MessageEvent e) =>
{
    var result = e.DataAs<string>();
    Console.WriteLine($"Worker says: {result}");
    e.Dispose();
};
worker.OnMessage += onMessage;

// Listen for errors in the worker
Action<Event> onError = (Event e) =>
{
    Console.WriteLine("Worker error occurred");
    e.Dispose();
};
worker.OnError += onError;

// Send a message to the worker
worker.PostMessage("start processing");

// Send structured data
worker.PostMessage(new { action = "compute", value = 42 });

// Send a message with transferable objects (zero-copy transfer)
using var buffer = new ArrayBuffer(1024);
worker.PostMessage(
    new { type = "data", buffer = buffer },
    new object[] { buffer }
);

// Create a worker with options (e.g., module type)
using var moduleWorker = new Worker("/js/module-worker.js", new WorkerOptions
{
    Type = "module"
});

// Clean up event handlers
worker.OnMessage -= onMessage;
worker.OnError -= onError;

// Terminate the worker immediately
worker.Terminate();