How to create a Web Worker from a string
I agree with the current accepted answer but often editing and managing the worker code will be hectic as its in the form of a string.
So optionally we can use the below approach where we can keep the worker as a function, and then covert to string->blob:
// function to be your worker
function workerFunction() {
var self = this;
self.onmessage = function(e) {
console.log('Received input: ', e.data); // message received from main thread
self.postMessage("Response back to main thread");
}
}
///////////////////////////////
var dataObj = '(' + workerFunction + ')();'; // here is the trick to convert the above fucntion to string
var blob = new Blob([dataObj.replace('"use strict";', '')]); // firefox adds "use strict"; to any function which might block worker execution so knock it off
var blobURL = (window.URL ? URL : webkitURL).createObjectURL(blob, {
type: 'application/javascript; charset=utf-8'
});
var worker = new Worker(blobURL); // spawn new worker
worker.onmessage = function(e) {
console.log('Worker said: ', e.data); // message received from worker
};
worker.postMessage("some input to worker"); // Send data to our worker.
This is tested in IE11+ and FF and Chrome
Summary
blob:
for Chrome 8+, Firefox 6+, Safari 6.0+, Opera 15+data:application/javascript
for Opera 10.60 - 12eval
otherwise (IE 10+)
URL.createObjectURL(<Blob blob>)
can be used to create a Web worker from a string. The blob can be created using the BlobBuilder
API deprecated or the Blob
constructor.
Demo: http://jsfiddle.net/uqcFM/49/
// URL.createObjectURL
window.URL = window.URL || window.webkitURL;
// "Server response", used in all examples
var response = "self.onmessage=function(e){postMessage('Worker: '+e.data);}";
var blob;
try {
blob = new Blob([response], {type: 'application/javascript'});
} catch (e) { // Backwards-compatibility
window.BlobBuilder = window.BlobBuilder || window.WebKitBlobBuilder || window.MozBlobBuilder;
blob = new BlobBuilder();
blob.append(response);
blob = blob.getBlob();
}
var worker = new Worker(URL.createObjectURL(blob));
// Test, used in all examples:
worker.onmessage = function(e) {
alert('Response: ' + e.data);
};
worker.postMessage('Test');
Compatibility
Web workers are supported in the following browsers source:
- Chrome 3
- Firefox 3.5
- IE 10
- Opera 10.60
- Safari 4
This method's support is based on the support of the Blob
API and the URL.createObjectUrl
method. Blob
compatibility:
- Chrome 8+ (
WebKitBlobBuilder
), 20+ (Blob
constructor) - Firefox 6+ (
MozBlobBuilder
), 13+ (Blob
constructor) - Safari 6+ (
Blob
constructor)
IE10 supports MSBlobBuilder
and URL.createObjectURL
. However, trying to create a Web Worker from a blob:
-URL throws a SecurityError.
Opera 12 does not support URL
API. Some users may have a fake version of the URL
object, thanks to this hack in browser.js
.
Fallback 1: data-URI
Opera supports data-URIs as an argument to the Worker
constructor. Note: Do not forget to escape special characters (Such as #
and %
).
// response as defined in the first example
var worker = new Worker('data:application/javascript,' +
encodeURIComponent(response) );
// ... Test as defined in the first example
Demo: http://jsfiddle.net/uqcFM/37/
Fallback 2: Eval
eval
can be used as a fallback for Safari (<6) and IE 10.
// Worker-helper.js
self.onmessage = function(e) {
self.onmessage = null; // Clean-up
eval(e.data);
};
// Usage:
var worker = new Worker('Worker-helper.js');
// `response` as defined in the first example
worker.postMessage(response);
// .. Test as defined in the first example