| title | short-title | slug | page-type | browser-compat |
|---|---|---|---|---|
MessageChannel: port2 property |
port2 |
Web/API/MessageChannel/port2 |
web-api-instance-property |
api.MessageChannel.port2 |
{{APIRef("Channel Messaging API")}} {{AvailableInWorkers}}
The port2 read-only property of the
{{domxref("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 {{domxref("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
{{domxref("MessageChannel.MessageChannel", "MessageChannel()")}} constructor. When the
IFrame has loaded, we pass port2 to the IFrame using
{{domxref("MessagePort.postMessage")}} along with a message. The
handleMessage handler then responds to a message being sent back from the
IFrame (using {{domxref("MessagePort.message_event", "onmessage")}}), putting it into a paragraph.
{{domxref("MessageChannel.port1", "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}}
{{Compat}}