Summary

• blob: for Chrome 8+, Firefox 6+, Safari 6.0+, Opera 15+


• data:application/javascript for Opera 10.60 - 12


• eval 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