ServiceWorkerState - Web APIs
the serviceworkerstate is associated with its serviceworker's state.
... specifications specification status comment service workersthe definition of 'serviceworkerstate' in that specification.

Using Fetch - Web APIs
ookie')); // false myheaders.set('content-type', 'text/html'); myheaders.append('x-custom-header', 'anothervalue'); console.log(myheaders.get('content-length')); // 11 console.log(myheaders.get('x-custom-header')); // ['processthisimmediately', 'anothervalue'] myheaders.delete('x-custom-header'); console.log(myheaders.get('x-custom-header')); // [ ] some of these operations are only useful in serviceworkers, but they provide a much nicer api for manipulating headers.
... immutable: mostly used for serviceworkers; renders a headers object read-only.
...similarly, inserting set-cookie into a response header is not allowed: serviceworkers are not allowed to set cookies via synthesized responses.
... they can also be created programmatically via javascript, but this is only really useful in serviceworkers, when you are providing a custom response to a received request using a respondwith() method: const mybody = new blob(); addeventlistener('fetch', function(event) { // serviceworker intercepting a fetch event.respondwith( new response(mybody, { headers: { 'content-type': 'text/plain' } }) ); }); the response() constructor takes two optional arguments — a body for the res...

Index - Web APIs
624 client api, client, experimental, interface, reference, service workers, service worker api, serviceworkerclient, serviceworkers the client interface represents an executable context such as a worker, or a sharedworker.
... 3993 serviceworkerstate api, interface, reference, service workers, serviceworkerstate the serviceworkerstate is associated with its serviceworker's state.

Request.mode - Web APIs
if any serviceworkers intercept these requests, they may not add or override any headers except for those that are simple headers.
...this ensures that serviceworkers do not affect the semantics of the web and prevents security and privacy issues arising from leaking data across domains.

Firefox and the "about" protocol
see firefox reader view for clutter-free web pages about:rights displays rights information about:robots special page showing notes about robots about:serviceworkers displays currently running service workers about:studies lists the shield studies that are installed about:sessionrestore session restoration (displayed after a firefox crash) about:support troubleshooting information (also available through firefox menu > ?

about:debugging (before Firefox 68) - Firefox Developer Tools
if the dom.serviceworkers.enable preference is set to false in about:config.

about:debugging - Firefox Developer Tools
service workers can be unavailable if the dom.serviceworkers.enable preference is set to false in about:config.

Request() - Web APIs
content-type': 'image/jpeg' }, mode: 'cors', cache: 'default' }; var myrequest = new request('flowers.jpg', myinit); you may also pass a request object to the request() constructor to create a copy of the request (this is similar to calling the clone() method.) var copy = new request(myrequest); note: this last usage is probably only useful in serviceworkers.

Response.error() - Web APIs
note: this is mainly relevant to serviceworkers; the error method is used to return an error if you so wish it.

Response.useFinalURL - Web APIs
this property applies only to serviceworkers.

ServiceWorker.state - Web APIs
syntax someurl = serviceworker.state value a serviceworkerstate definition (see the spec.) examples this code snippet is from the service worker registration-events sample (live demo).

Using Service Workers - Web APIs
if however you find that demo code is not working in your installed versions, you might need to enable a pref: firefox nightly: go to about:config and set dom.serviceworkers.enabled to true; restart browser.

Service Worker API - Web APIs
serviceworkerstate associated with its serviceworker's state.

Using Web Workers - Web APIs
other types of worker in addition to dedicated and shared web workers, there are other types of worker available: serviceworkers essentially act as proxy servers that sit between web applications, and the browser and network (when available).

Web Workers API - Web APIs
serviceworkers essentially act as proxy servers that sit between web applications, the browser, and the network (when available).