Worker: message event

The message event is fired on a Worker object when the worker's parent receives a message from its worker (i.e. when the worker sends a message using DedicatedWorkerGlobalScope.postMessage()).

Bubbles No
Cancelable No
Interface MessageEvent
Event handler property onmessage

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 Status
HTML Living Standard Living Standard

Browser compatibility

BCD tables only load in the browser

See also