MessageChannel: port2 property

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.

Value

A MessagePort object representing the second port of the channel, the port attached to the context at the other end of 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 port2 to the IFrame using Window.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. port1 is listened to, to check 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;
}

For a full working example, see our channel messaging basic demo on GitHub (run it live too).

Specifications

Browser compatibility

See also

• Using channel messaging