service worker: client.postMessage() is buffered until the document is ready.

Category: Service Worker
Type: New or changed feature
Status: Enabled by default (Chrome 74)
Intent stage: None

Summary

To prevent messages from being delivered before the destination is ready, client.postMessage() does not dispatch the message until one of the following has occurred on the destination: - 'DOMContentLoaded' event is fired. - onmessage is set. - startMessages() is called.

Standards & signals

Specification: https://w3c.github.io/ServiceWorker/#dfn-client-message-queue
Firefox: Shipped/Shipping
Safari: No signal
Web developers: No signals
Tracking bug: https://crbug.com/915685

Docs: https://w3c.github.io/ServiceWorker/#dfn-client-message-queue

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