The onmessage
event handler of the MessagePort
interface is an EventListener
, called whenever an MessageEvent
of type message
is fired on the port — that is, when the port receives a message.
Note: This feature is available in Web Workers.
Syntax
channel.onmessage = function() { ... };
Example
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 MessageChannel.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.
var channel = new MessageChannel();
var para = document.querySelector('p');
var ifr = document.querySelector('iframe');
var 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 ([[../../../../../../../mdn.github.io/channel-messaging-basic-demo/index|run it live too]]).
Specifications
Specification | Status | Comment |
HTML Living StandardThe definition of 'onmessage' in that specification. | Living Standard |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
onmessage
|
Chrome
Full support 4 |
Edge
Full support 12 |
Firefox
Full support Yes |
IE
Full support 10 |
Opera
Full support 10.6 |
Safari
Full support 5 |
WebView Android
Full support Yes |
Chrome Android
Full support 18 |
Firefox Android
No support No |
Opera Android
Full support 11 |
Safari iOS
Full support 5.1 |
Samsung Internet Android
Full support 1.0 |
Legend
- Full support
- Full support
- No support
- No support
See also
MessagePort.onmessage by Mozilla Contributors is licensed under CC-BY-SA 2.5.