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.
A MessagePort
object representing the second port of the channel, the port attached to the context at the other end of the channel.
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 onmessage
), putting it into a paragraph. MessageChannel.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).