Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("message", (event) => { })
onmessage = (event) => { }

Event type

A MessageEvent. Inherits from Event.

Examples

This code creates a new worker and listens to messages from it using addEventListener():

const worker = new Worker("static/scripts/worker.js");
worker.addEventListener("message", (event) => {
  console.log(`Received message from worker: ${event.data}`);
});

Alternatively, it could listen using the onmessage event handler property:

const worker = new Worker("static/scripts/worker.js");
worker.onmessage = (event) => {
  console.log(`Received message from worker: ${event.data}`);
};

The worker posts messages using self.postMessage():

// static/scripts/worker.js
self.postMessage("I'm alive!");

Specifications

Specification
HTML # event-message

Browser compatibility

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This page was last modified on Jul 28, 2026 by MDN contributors.