MessagePort: messageerror event

Syntax

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

addEventListener("messageerror", (event) => { })

onmessageerror = (event) => { }

Event type

A MessageEvent. Inherits from Event.

Event properties

This interface also inherits properties from its parent, Event.

MessageEvent.data Read only

The data sent by the message emitter.

MessageEvent.origin Read only

A string representing the origin of the message emitter.

MessageEvent.lastEventId Read only

A string representing a unique ID for the event.

MessageEvent.source Read only

A MessageEventSource (which can be a WindowProxy, MessagePort, or ServiceWorker object) representing the message emitter.

MessageEvent.ports Read only

An array containing all MessagePort objects sent with the message, in order.

Examples

Attempting to share memory

A common cause of messageerror events is attempting to send a SharedArrayBuffer object, or a buffer view backed by one, across agent clusters. For example, a window is not in the same agent cluster as a shared worker it created, so suppose the page runs the following code:

const worker = new SharedWorker("worker.js");
worker.port.start();
worker.port.addEventListener("message", (event) => {
  worker.port.postMessage(new SharedArrayBuffer(1024));
});

And worker.js contains the following code:

self.addEventListener("connect", (event) => {
  console.log("Hello");
  const port = event.ports[0];
  port.start();
  port.postMessage("Port connected");
  port.addEventListener("messageerror", (event) => {
    console.log("Message error");
  });
});

Then the shared worker will receive a messageerror event when it tries to deserialize the message sent from the window.

Specifications

Browser compatibility

See also

• Related events: message.
• Using channel messaging