MessageChannel: port2 property
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.
Note: This feature is available in Web Workers.
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
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.
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
Specification |
---|
HTML Standard # dom-messagechannel-port2-dev |
Browser compatibility
BCD tables only load in the browser