JavaScript: The Definitive Guide, 6th Edition

Name

Worker — a worker thread

Inherits from

EventTarget

Synopsis

A Worker represents a background thread. Create a new Worker with the Worker() constructor, passing the URL of a file of JavaScript code for it to run. The JavaScript code in that file can use synchronous APIs or perform compute-intensive tasks without freezing up the main UI thread. Workers run their code in a completely separate execution context (see WorkerGlobalScope), and the only way to exchange data with a worker is via asynchronous events. Call postMessage() to send data to the Worker, and handle message events to receive data from the worker.

See Web Workers for an introduction to worker threads.

Constructor

new Worker(string scriptURL)

Constructs a new Worker object and causes it to run the JavaScript code in scriptURL.

Methods

void postMessage(any message, [MessagePort[] ports])

Send message to the worker, which will receive it as a MessageEvent object sent to its on message handler. message can be a JavaScript primitive value or object or array, but not a function. Client-side types ArrayBuffer, File, Blob, and ImageData are allowed, but Nodes, such as Document and Element, are not allowed (see Structured Clones for details).

The optional ports argument is an advanced feature that allows you to pass one or more direct communication channels to the Worker. If you create two Worker objects, for example, you can allow them to communicate directly with each other by passing them each one end of a MessageChannel.

void