MessageChannel.port1

The port1 read-only property of the MessageChannel interface returns the first port of the message channel — the port attached to the context that originated the channel.

Note: This feature is available in Web Workers.

Syntax

channel.port1;

Value

A MessagePort object, the first port of the channel, that is the port attached to the context that originated the channel.

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 a message being sent back from the <iframe> (using MessagePort.onmessage), putting it into a paragraph. The handleMessage method is associated to the port1 to listen when the message arrives.

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;
}

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'port1' in that specification.
Living Standard

Browser compatibility

BCD tables only load in the browser

See also