MessageChannel()

The MessageChannel() constructor of the MessageChannel interface returns a new MessageChannel object with two new MessagePort objects.

Note: This feature is available in Web Workers

Syntax

new MessageChannel()

Parameters

None (undefined).

Return value

A new MessageChannel object.

Examples

In the following code block, you can see a new channel being created using the MessageChannel.MessageChannel constructor. When the <iframe> has loaded, we pass port2 to the <iframe> using MessagePort.postMessage along with a message. The handleMessage handler then responds to a message being sent back from the <iframe> (using onmessage), putting it into a paragraph. The port1 is listened to, to check when the message arrives.

const channel = new MessageChannel();
const para = document.querySelector('p');

const ifr = document.querySelector('iframe');
const 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
HTML Standard
# dom-messagechannel-dev

Browser compatibility

BCD tables only load in the browser

See also