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The Worker() constructor creates a Worker object that executes the script at the specified URL. This script must obey the same-origin policy.

If the URL has an invalid syntax or if the same-origin policy is violated a DOMException of type SECURITY_ERR is thrown.

Note: that there is a disagreement among browser manufacturers about whether a data URI is of the same origin or not. Though Gecko 10.0 (Firefox 10.0 / Thunderbird 10.0 / SeaMonkey 2.7) and later accept data URIs, that's not the case in all other browsers.

Syntax

var myWorker = new Worker(aURL, options);

Parameters

aURL
A USVString representing the URL of the script the worker will execute. It must obey the same-origin policy.
options Optional
An object containing option properties that can be set when creating the object instance. Available properties are as follows:
  • type: A DOMString specifying the type of worker to create. The value can be classic or module. If not specified, the default used is classic.
  • credentials: A DOMString specifying the type of credentials to use for the worker. The value can be omit, same-origin, or include. If not specified, or if type is classic, the default used is omit (no credentials required).
  • name: A DOMString specifying an identifying name for the DedicatedWorkerGlobalScope representing the scope of the worker, which is mainly useful for debugging purposes.

Exceptions

  • A SecurityError is raised if the document is not allowed to start workers.
  • A NetworkError is raised if the MIME type of one of the script is text/csv, image/*, video/*, or audio/*. It should always be text/javacript.
  • A SyntaxError is raised if aURL cannot be parsed.

Example

The following code snippet shows creation of a Worker object using the Worker() constructor and subsequent usage of the object:

var myWorker = new Worker('worker.js');

first.onchange = function() {
  myWorker.postMessage([first.value,second.value]);
  console.log('Message posted to worker');
}

For a full example, see ourBasic dedicated worker example (run dedicated worker).

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'Worker()' in that specification.
Living Standard  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 4 3.5 10.0 10.6 4
name option (Yes) 55 (55) ? ? ?
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support 4.4 3.5 10.0 11.5 5.1
name option ? 55.0 (55) ? ? ?

See also

The Worker interface it belongs to.

Document Tags and Contributors

 Contributors to this page: weeking, DomenicDenicola, chrisdavidmills, nmve, teoli, Jeremie, kscarfone
 Last updated by: weeking,