{"json_modified": "2016-09-25T03:12:14.230533", "uuid": "3beddfd2-9dc3-4626-aec8-9df29d25ac41", "title": "PromiseWorker.jsm", "url": "/en-US/docs/Mozilla/JavaScript_code_modules/PromiseWorker.jsm", "tags": ["Extensions", "Workers", "NeedsContent", "Guide", "API", "js-ctypes", "Add-ons", "add-ons"], "translations": [], "modified": "2016-09-25T03:12:14", "label": "PromiseWorker.jsm", "localization_tags": [], "locale": "en-US", "id": 156291, "last_edit": "2016-09-25T03:12:06", "summary": "A <code>PromiseWorker</code> is a <a href=\"/en-US/docs/Web/API/ChromeWorker\" title=\"If you're developing privileged code, and would like to create a worker that can use js-ctypes to perform calls to native code, you can do so by using ChromeWorker instead of the standard Worker object. It works exactly like a standard Worker, except that it has access to js-ctypes via a global ctypes object available in the global scope of the worker. Examples of ChromeWorker's using js-ctypes are availabe on Github and are linked to from the See Also section below. To use a postMessage with callback version of ChromeWorker that features promises, see PromiseWorker.\"><code>ChromeWorker</code></a> except instead of calling <code>postMessage()</code> to send a message, you call <code>post()</code>, which returns a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise\" title=\"The Promise object is used for asynchronous computations. A Promise represents a value which may be available now, or in the future, or never.\"><code>Promise</code></a>. JavaScript files imported into the worker scope and main thread scope which allows posting to the worker and receiving in the form of a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise\" title=\"The Promise object is used for asynchronous computations. A Promise represents a value which may be available now, or in the future, or never.\">promise</a>. Like\u00a0<code>ChromeWorker</code> objects, <code>PromiseWorker</code> is mostly used for <a href=\"/en-US/docs/Mozilla/js-ctypes\">js-ctypes</a> but it is not limited to that. There is no <a href=\"/en-US/docs/Mozilla/Tech/XPCOM/Guide/Creating_components/An_Overview_of_XPCOM\">XPCOM</a> access, similar to <code>ChromeWorker</code>. This answers the question \"When should I use a <code>PromiseWorker</code>?\", and the answer is, whenever you would normally use a <code>ChromeWorker</code>, but want <code>postMessage</code> to return promises.", "sections": [{"id": "Summary", "title": "Summary"}, {"id": "PromiseWorker.jsm", "title": "PromiseWorker.jsm"}, {"id": "PromiseWorker.js", "title": "PromiseWorker.js"}, {"id": "Setup_and_usage", "title": "Setup and usage"}, {"id": "Worker_file", "title": "Worker file"}, {"id": "Main_thread_file", "title": "Main thread file"}, {"id": "Sending_a_message_from_main_thread", "title": "Sending a message from main thread"}, {"id": "post", "title": null}, {"id": "Syntax", "title": "Syntax"}, {"id": "Parameters", "title": "Parameters"}, {"id": "Returns", "title": "Returns"}, {"id": "Transferring_special_data_from_main_thread_to_worker", "title": "Transferring special data from main thread to worker"}, {"id": "aTransferList", "title": "aTransferList"}, {"id": "BasePromiseWorker.Meta", "title": "BasePromiseWorker.Meta"}, {"id": "Sending_a_message_from_worker", "title": "Sending a message from worker"}, {"id": "Resolving_the_Promise", "title": "Resolving the Promise"}, {"id": "Transferring_special_data_from_worker_to_main_thread", "title": "Transferring special data from worker to main thread"}, {"id": "Rejecting_the_Promise", "title": "Rejecting the Promise"}, {"id": "Catching_the_Promise", "title": "Catching the Promise"}, {"id": "Complete_example", "title": "Complete example"}, {"id": "Worker_file_2", "title": "Worker file"}, {"id": "myWorker.js", "title": null}, {"id": "Main_thread_file_2", "title": "Main thread file"}, {"id": "bootstrap.js", "title": "bootstrap.js"}, {"id": "Result", "title": "Result"}, {"id": "Other_examples", "title": "Other examples"}, {"id": "See_also", "title": "See also"}], "slug": "Mozilla/JavaScript_code_modules/PromiseWorker.jsm", "review_tags": ["technical"]}