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 Status
HTML Living Standard Living Standard

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
messageerror eventChrome Full support 60Edge Full support 18Firefox Full support 57IE ? Opera Full support 47Safari ? WebView Android Full support 60Chrome Android Full support 60Firefox Android Full support 57Opera Android Full support 47Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also