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MessageChannel: port1 property

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

Value

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

Examples

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 onmessage), putting it into a paragraph. The handleMessage method is associated to the port1 to listen when the message arrives.

js

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;
}

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
port1 2 12 41 10 10.6 5 4.4 18 41 11 4.2 1.0

See also

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https://developer.mozilla.org/en-US/docs/Web/API/MessageChannel/port1