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

js

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

onmessageerror = (event) => { }

In addition to the properties listed below, properties from the parent interface, Event, are available.

data Read only

The data sent by the message emitter.

origin Read only

A string representing the origin of the message emitter.

lastEventId Read only

A string representing a unique ID for the event.

source Read only

A message event source, which is either a WindowProxy, a MessagePort, or a ServiceWorker object representing the message emitter.

ports Read only

An array of MessagePort objects representing the ports associated with the channel the message is being sent through (where appropriate, e.g., in channel messaging or when sending a message to a shared worker).

This code uses addEventListener() to listen for messages and errors:

js

const channel = new BroadcastChannel("example-channel");

channel.addEventListener("message", (event) => {
  received.textContent = event.data;
});

channel.addEventListener("messageerror", (event) => {
  console.error(event);
});

The same, but using the onmessage and onmessageerror event handler properties:

js

const channel = new BroadcastChannel("example-channel");

channel.onmessage = (event) => {
  received.textContent = event.data;
};

channel.onmessageerror = (event) => {
  console.log(event);
};

A common cause of messageerror events is attempting to send a SharedArrayBuffer object, or a buffer view backed by one, across agent clusters. The following code demonstrates this.

Page A runs the following code:

js

const channel = new BroadcastChannel("hello");
channel.postMessage({ data: new SharedArrayBuffer(1024) });

Page B runs the following code:

js

const channel = new BroadcastChannel("hello");
channel.addEventListener("messageerror", (event) => {
  console.error("Message error");
});

Then page B will receive a messageerror event when it tries to deserialize the message sent from page A.