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

undefined.

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

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