Web/API/ExtendableMessageEvent/source

The source read-only property of the ExtendableMessageEvent interface returns a reference to the Client object from which the message was sent.

Syntax

var mySource = extendableMessageEvent.source;

Value

A Client, ServiceWorker or MessagePort object.

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.

var port;

self.addEventListener('push', function(e) {
  var 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 = function(e) {
  console.log(e.source);
  port = e.ports[0];
}

Specifications

Specification	Status	Comment
Service WorkersThe definition of 'ExtendableMessageEvent.source' in that specification.	Working Draft	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`source` Experimental'	Chrome ?	Edge ?	Firefox Full support 45 Notes' Full support 45 Notes' Notes' Extended Support Releases (ESR) before Firefox 78 ESR do not support service workers and the Push API.	IE No support No	Opera ?	Safari No support No	WebView Android No support No	Chrome Android ?	Firefox Android Full support 45	Opera Android ?	Safari iOS No support No	Samsung Internet Android ?

Legend

Full support: Full support
No support: No support
Compatibility unknown: Compatibility unknown
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.
See implementation notes.': See implementation notes.