The MessageChannel interface of the Channel Messaging API allows us to create a new message channel and send data through it via its two MessagePort properties.

Note: This feature is available in Web Workers.

Properties

MessageChannel.port1 Read only
Returns port1 of the channel.
MessageChannel.port2 Read only
Returns port2 of the channel.

Constructor

MessageChannel()

Returns a new MessageChannel object with two new MessagePort objects.

Example

In the following code block, you can see a new channel being created using the MessageChannel() constructor. When the <iframe> has loaded, we pass MessageChannel.port2 to the <iframe> using MessagePort.postMessage along with a message. The handleMessage handler then responds to the message being sent back from the <iframe> (using MessagePort.onmessage), by putting it into a paragraph.

var channel = new MessageChannel();
var para = document.querySelector('p');
    
var ifr = document.querySelector('iframe');
var otherWindow = ifr.contentWindow;

ifr.addEventListener("load", iframeLoaded, false);
    
function iframeLoaded() {
  otherWindow.postMessage('Hello from the main page!', '*', [channel.port2]);
}

channel.port1.onmessage = handleMessage;
function handleMessage(e) {
  para.innerHTML = e.data;
}   

For a full working example, see our channel messaging basic demo on Github (run it live too).

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'Message channels' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support4 Yes411010.65
MessageChannel4 Yes411010.65
port14 Yes411010.65
port24 Yes411010.65
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support4.44 Yes4111.55.1 ?
MessageChannel4.44 Yes4111.55.1 ?
port14.44 Yes4111.55.1 ?
port24.44 Yes4111.55.1 ?

See also

Document Tags and Contributors

Last updated by: fscholz,