MessageChannel.port2

The port2 read-only property of the MessageChannel interface returns the second port of the message channel — the port attached to the context at the other end of the channel, which the message is initially sent to.

Note: This feature is available in Web Workers.

Syntax

channel.port2;

Value

A MessagePort object representing the second port of the channel, the port attached to the context at the other end of the channel.

Example

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 MessagePort.onmessage), putting it into a paragraph. MessageChannel.port1 is listened to, to check 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;
}   

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 'port2' in that specification.
Living Standard  

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
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 18Firefox Android Full support 41Opera Android Full support 11Safari iOS Full support 5.1Samsung Internet Android Full support Yes

Legend

Full support  
Full support

See also