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 (run it live too).
Specifications
Specification | Status | Comment |
---|---|---|
HTML Living Standard The 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.
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