Web/API/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 StandardThe definition of 'port1' in that specification.	Living Standard

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`port1`	Chrome Full support 4	Edge Full support 12	Firefox Full support 41	IE Full support 10	Opera Full support 10.6	Safari Full support 5	WebView Android Full support 4.4	Chrome Android Full support 18	Firefox Android Full support 41	Opera Android Full support 11	Safari iOS Full support 5.1	Samsung Internet Android Full support 1.0

Legend

Full support: Full support