ServiceWorkerContainer: startMessages() method
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
Note: This feature is available in Web Workers.
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 onmessage. In this you
don't need startMessages().
Syntax
startMessages()
Parameters
None.
Return value
undefined.
Examples
if ("serviceWorker" in navigator) {
navigator.serviceWorker.register("/sw.js").then(() => {
console.log("Service Worker Registered");
});
}
// …
navigator.serviceWorker.addEventListener("message", (e) => {
// …
});
navigator.serviceWorker.startMessages();
Specifications
| Specification |
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| Service Workers Nightly # navigator-service-worker-startMessages |
Browser compatibility
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startMessages
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Legend
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- Full support
- Full support
- No support
- No support