Worker: message event
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Note: This feature is available in Web Workers, except for Service Workers.
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()).
This event is not cancellable and does not bubble.
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
See also
- Related events:
messageerror. DedicatedWorkerGlobalScope.postMessage().