MessageChannel: port1 property - Web APIs | MDN (original) (raw)

Baseline

Widely available

Note: This feature is available in Web Workers.

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

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 theMessageChannel() constructor. When the has loaded, we pass port2 to the 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 theport1 to listen when the message arrives.

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

See also