MessageChannel: MessageChannel() constructor
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 MessageChannel() constructor of the MessageChannel
interface returns a new MessageChannel object with two new
MessagePort objects.
Syntax
new MessageChannel()
Parameters
None (undefined).
Return value
A new MessageChannel object.
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.
The 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 # dom-messagechannel-dev |
Browser compatibility
| desktop | mobile | server | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
MessageChannel() constructor | ||||||||||||||