MessagePort: messageerror event

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

Bubbles No
Cancelable No
Interface MessageEvent
Event handler property onmessageerror

Examples

Suppose a script creates a MessageChannel and sends one of the ports to a different browsing context, such as another <iframe>, using code like this:

const channel = new MessageChannel();
const myPort = channel.port1;
const targetFrame = window.top.frames[1];
const targetOrigin = 'https://example.org';

const messageControl = document.querySelector('#message');
const channelMessageButton = document.querySelector('#channel-message');

channelMessageButton.addEventListener('click', () => {
    myPort.postMessage(messageControl.value);
})

targetFrame.postMessage('init', targetOrigin, [channel.port2]);

The target can receive the port and start listening for messages and message errors on it using code like this:

window.addEventListener('message', (event) => {
    const myPort = event.ports[0];

    myPort.addEventListener('message', (event) => {
        received.textContent = event.data;
    });

    myPort.addEventListener('messageerror', (event) => {
        console.error(event.data);
    });

    myPort.start();
});

Note that the listener must call MessagePort.start() before any messages will be delivered to this port. This is only needed when using the addEventListener() method: if the receiver uses onmessage instead, start() is called implicitly:

window.addEventListener('message', (event) => {
    const myPort = event.ports[0];

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

    myPort.onmessageerror = (event) => {
        console.error(event.data);
    };

});

Specifications

Specification
HTML Standard (HTML)
# event-messageerror

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
messageerror_event
60
18
57
No
47
No
60
60
57
47
No
8.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/MessagePort/messageerror_event