Web worker

A web worker, as defined by the World Wide Web Consortium (W3C) and the Web Hypertext Application Technology Working Group (WHATWG), is a JavaScript script executed from an HTML page that runs in the background, independently of scripts that may also have been executed from the same HTML page. Web workers are often able to utilize multi-core CPUs more effectively. The W3C and WHATWG envision web workers as long-running scripts that are not interrupted by scripts that respond to clicks or other user interactions. Keeping such workers from being interrupted by user activities should allow Web pages to remain responsive at the same time as they are running long tasks in the background. The web worker specification is part of the HTML Living Standard.

A web worker, as defined by the World Wide Web Consortium (W3C) and the Web Hypertext Application Technology Working Group (WHATWG), is a JavaScript script executed from an HTML page that runs in the background, independently of scripts that may also have been executed from the same HTML page. Web workers are often able to utilize multi-core CPUs more effectively. The W3C and WHATWG envision web workers as long-running scripts that are not interrupted by scripts that respond to clicks or other user interactions. Keeping such workers from being interrupted by user activities should allow Web pages to remain responsive at the same time as they are running long tasks in the background. The web worker specification is part of the HTML Living Standard. var worker = new Worker("worker_script.js"); To send a message to the worker, the postMessage method of the worker object is used as shown below. worker.postMessage("Hello World!"); The onmessage property uses an event handler to retrieve information from a worker. worker.onmessage = function(event) { alert("Received message " + event.data); doSomething(); } function doSomething() { //do work worker.postMessage("Work done!"); } worker.terminate(); Once a worker is terminated, it goes out of scope and the variable referencing it becomes undefined; at this point a new worker has to be created if needed. Worker example: One-core computation The highest prime number discovered so far is: var worker = new Worker('worker.js'); worker.onmessage = function (event) { document.getElementById('result').textContent = event.data; }; The Worker() constructor call creates a web worker and returns a worker object representing that web worker, which is used to communicate with the web worker. That object's onmessage event handler allows the code to receive messages from the web worker. The Web Worker itself is as follows: var n = 1; var end_value = 10**7; search: while (n To send a message back to the page, the postMessage() method is used to post a message when a prime is found. function browserSupportsWebWorkers() { return typeof window.Worker === "function"; } Web workers are currently supported by Chrome, Opera, Edge, Internet Explorer (version 10), Mozilla Firefox, and Safari. Mobile Safari for iOS has supported web workers since iOS 5. The Android browser first supported web workers in Android 2.1, but support was removed in Android versions 2.2–4.3 before being restored in Android 4.4. ==See also== Web service worker ==References== ==External links== Web Workers – W3C Web Workers – WHATWG Using Web Workers – Mozilla Developer Network

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