ExtendableMessageEvent: ports property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2018.

Note: This feature is only available in Service Workers.

The ports read-only property of the ExtendableMessageEvent interface returns the array containing the MessagePort objects representing the ports of the associated message channel (the channel the message is being sent through.)

Value

An array of MessagePort objects.

Examples

When the following code is used inside a service worker to respond to a push messages by sending the data received via PushMessageData to the main context via a channel message, the event object of onmessage will be a ExtendableMessageEvent.

js
let port;

self.addEventListener("push", (e) => {
  const obj = e.data.json();

  if (obj.action === "subscribe" || obj.action === "unsubscribe") {
    port.postMessage(obj);
  } else if (obj.action === "init" || obj.action === "chatMsg") {
    port.postMessage(obj);
  }
});

self.onmessage = (e) => {
  port = e.ports[0];
};

Specifications

Specification
Service Workers
# extendablemessage-event-ports

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
ports

Legend

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Full support
Full support
No support
No support

See also