MessagePort: messageerror event

The messageerror event is fired on a MessagePort object when it receives a message that can't be deserialized.

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("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