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;
}

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 'port1' 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 ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Last updated by: sideshowbarker,