ExtendableMessageEvent.lastEventId

The lastEventID read-only property of the ExtendableMessageEvent interface represents, in server-sent events, the last event ID of the event source. This is an empty string.

Syntax

var myLastEventId = extendableMessageEvent.lastEventId;

Value

A DOMString.

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.lastEventId);
  port = e.ports[0];
}

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
lastEventId
51
17
45
Extended Support Releases (ESR) before Firefox 78 ESR do not support service workers and the Push API.
No
38
11.1
51
51
45
41
11.3
5.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/ExtendableMessageEvent/lastEventId