ServiceWorkerMessageEvent.lastEventId

Deprecated
This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Avoid using it and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

Important: In modern browsers, this property has been deprecated. Service worker messages will now use the MessageEvent interface, for consistency with other web messaging features.

The lastEventID read-only property of the ServiceWorkerMessageEvent interface represents, in server-sent events, the last event ID of the event source.

Syntax

var myLastEventId = ServiceWorkerMessageEventInstance.lastEventId;

Value

A DOMString.

Examples

When the following code is used inside the main thread to set up a message channel between it and a service worker for sending messages between the two, the event object of onmessage will be a ServiceWorkerMessageEvent.

navigator.serviceWorker.ready.then(function(reg) {  

  ...

      // set up a message channel to communicate with the SW
      var channel = new MessageChannel();
      channel.port1.onmessage = function(e) {
        console.log(e.lastEventId);
        handleChannelMessage(e.data);
      }
      
      mySW = reg.active;
      mySW.postMessage('hello', [channel.port2]);
  });

Specifications

Specification Status Comment
Service Workers
The definition of 'ServiceWorkerMessageEvent.lastEventId' in that specification.
Working Draft Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support45

17

161

44 — 552 3 No24 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No45 ?44 — 5524 No4.0

1. From version 16: this feature is behind the Enable service workers preference.

2. Service workers (and Push) have been disabled in the Firefox 45 and 52 Extended Support Releases (ESR).

3. In Firefox 55 and later, the standard MessageEvent interface must be used instead.

See also

Document Tags and Contributors

Contributors to this page: fscholz, abbycar, chrisdavidmills, narohcp
Last updated by: fscholz,