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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 example, you can see a new channel being created using the MessageChannel.MessageChannel constructor.

When the IFrame has loaded, we register an onmessage handler for  MessageChannel.port1 and transfer MessageChannel.port2 to the IFrame using the window.postMessage method along with a message.

When a message is received back from the IFrame, the onMessage function simply outputs the message to a paragraph.

var channel = new MessageChannel();
var output = document.querySelector('.output');
var iframe = document.querySelector('iframe');

// Wait for the iframe to load
iframe.addEventListener("load", onLoad);

function onLoad() {
  // Listen for messages on port1
  channel.port1.onmessage = onMessage;

  // Transfer port2 to the iframe
  iframe.contentWindow.postMessage('Hello from the main page!', '*', [channel.port2]);
}


// Handle messages received on port1
function onMessage(e) {
  output.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

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 4Edge Full support YesFirefox Full support 41IE Full support 10Opera Full support 10.6Safari Full support 5WebView Android Full support 4.4Chrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 41Opera Android Full support 11.5Safari iOS Full support 5.1Samsung Internet Android ?
MessageChannelChrome Full support 4Edge Full support YesFirefox Full support 41IE Full support 10Opera Full support 10.6Safari Full support 5WebView Android Full support 4.4Chrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 41Opera Android Full support 11.5Safari iOS Full support 5.1Samsung Internet Android ?
port1Chrome Full support 4Edge Full support YesFirefox Full support 41IE Full support 10Opera Full support 10.6Safari Full support 5WebView Android Full support 4.4Chrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 41Opera Android Full support 11.5Safari iOS Full support 5.1Samsung Internet Android ?
port2Chrome Full support 4Edge Full support YesFirefox Full support 41IE Full support 10Opera Full support 10.6Safari Full support 5WebView Android Full support 4.4Chrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 41Opera Android Full support 11.5Safari iOS Full support 5.1Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also