ServiceWorkerContainer.startMessages()

The startMessages() method of the ServiceWorkerContainer interface explicitly starts the flow of messages being dispatched from a service worker to pages under its control (e.g. sent via Client.postMessage()). This can be used to react to sent messages earlier, even before that page's content has finished loading.

Explanation

By default, all messages sent from a page's controlling service worker to the page (using Client.postMessage()) are queued while the page is loading, and get dispatched once the page's HTML document has been loaded and parsed (i.e. after the DOMContentLoaded event fires). It's possible to start dispatching these messages earlier by calling ServiceWorkerContainer.startMessages(), for example if you've invoked a message handler using EventTarget.addEventListener() before the page has finished loading, but want to start processing the messages right away.

Note: The messages start being sent automatically when setting the handler directly using ServiceWorkerContainer.onmessage. In this you don't need startMessages().

Syntax

ServiceWorkerContainer.startMessages();

Parameters

None.

Return value

Void.

Examples

if('serviceWorker' in navigator) {
  navigator.serviceWorker
           .register('/sw.js')
           .then(function() { console.log('Service Worker Registered'); });
}

// ...

navigator.serviceWorker.addEventListener('message', (e) => {
  // ...
});

navigator.serviceWorker.startMessages();

Specifications

Specification Status Comment
Service Workers
The definition of 'ServiceWorkerContainer: startMessages()' in that specification.
Working Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
startMessagesChrome Full support 74Edge ? Firefox Full support 64IE No support NoOpera Full support 61Safari Full support YesWebView Android Full support 74Chrome Android Full support 74Firefox Android Full support 64Opera Android Full support 50Safari iOS Full support YesSamsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

Document Tags and Contributors

Contributors to this page: jpmedley, mdnwebdocs-bot, philipwalton, chrisdavidmills
Last updated by: jpmedley,