[Edit ~5 years later: some of this is beginning to change, and there are new web platform features that actually allow rendering to a canvas from a Worker! See this blog for more info: https://hacks.mozilla.org/2016/01/webgl-off-the-main-thread/ – the rest of the answer is provided for 2011-era information ;)] Web workers can only calculate, not modify the … Read more
This is the way web workers are designed. They must have their own external JS file and their own environment initialized by that file. They cannot share an environment with your regular global JS space for multi-threading conflict reasons. One reason that web workers are not allowed direct access to your global variables is that … Read more
The answer given by sbr works, but it would cause a copy of the data to be made before being sent to the worker. That could be slow for a large amount of data. To use “transferable objects” you actually transfer the ownership of the object to or from the web worker. It’s like passing … Read more
Using var a in the function means that a will always be private. Since importScripts adds to the global scope, JS prefers to access the more localized a in the function that posts a. You can post self.a instead, which shall be 6, as you expected. EDIT: Someone recently asked me about this in person, … Read more
No you cannot. There’s no access to non-thread safe components or the DOM and you have to pass specific data in and out of a thread through serialized objects. So you have to work really hard to cause problems in your code. jQuery is a JavaScript DOM library. But you can use a native XMLHttpRequest … Read more
This is only as reliable as beforeunload, but seems to work (tested in Firefox and Chrome). I definitely favour it over a polling solution. // Tell the SharedWorker we’re closing addEventListener( ‘beforeunload’, function() { port.postMessage( {command:’closing’} ); }); Then handle the cleanup of the port object in the SharedWorker. e.ports[0].onmessage = function( e ) { … Read more
from config.h of Android 2.2. commit 68698168e7547cc10660828f1fb82be7a8efa845 Author: Steve Block Date: Wed Mar 17 14:37:19 2010 +0000 Disable workers This is because V8 on Android does not have the required locking. Also disables channel messaging, which is used only with workers. Bug: 2522239 Change-Id: I6cb91b4048c7e1a0351e422561625397a2e98986 via http://code.google.com/p/android/issues/detail?id=10004#c7
`Deferred/Promises and Web Workers address different needs: Deferred/promise are constructs to assign a reference to a result not yet available, and to organize code that runs once the result becomes available or a failure is returned. Web Workers perform actual work asynchronously (using operating system threads not processes – so they are relatively light weight). … Read more
Small update, as the question is now more than half a year old: In Chrome/Chromium 6 you can now send a canvas’ ImageData object to a web worker, let the web worker make changes to the object and then write it back to the canvas using putImageData(..). Google’s Chromabrush does it this way, the source-code … Read more
I’ve been fiddling with WebAssembly recently, and found a way to make it work. Here are the script files: main.js chrome.browserAction.onClicked.addListener(function(tab) { chrome.tabs.executeScript(null, {file: “content_script.js”}); }); content_script.js var importObject = { imports: { imported_func: arg => console.log(arg) } }; url=”data:application/wasm;base64,” + “AGFzbQEAAAABCAJgAX8AYAAAAhkBB2ltcG9ydHMNaW1wb3J0ZWRfZnVuYwAAAwIBAQcRAQ1leHBvcnRlZF9mdW5jAAEKCAEGAEEqEAAL”; WebAssembly.instantiateStreaming(fetch(url), importObject) .then(obj => obj.instance.exports.exported_func()); The data URL belongs to the common tutorial … Read more