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The lastEventId read-only property of the MessageEvent interface is a DOMString representing a unique ID for the event.


var myId = messageEvent.lastEventId;


A DOMString representing the ID.


myWorker.onmessage = function(e) {
  result.textContent = e.data;
  console.log('Message received from worker');


Specification Status Comment
The definition of 'lastEventId' in that specification.
Unknown Initial definition

Browser compatibility

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Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 1 (Yes) 4.0 (2.0) 9 ? 10.0+
Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? (Yes) ? ? ? 3.0+

See also

  • ExtendableMessageEvent — similar to this interface but used in interfaces that needs to give more flexibility to authors.

Document Tags and Contributors

 Contributors to this page: chrisdavidmills
 Last updated by: chrisdavidmills,