Window: message event
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The message
event is fired on a Window
object when the window receives a message, for example from a call to Window.postMessage()
from another browsing context.
This event is not cancellable and does not bubble.
Syntax
Use the event name in methods like addEventListener()
, or set an event handler property.
addEventListener("message", (event) => {});
onmessage = (event) => {};
Event type
A MessageEvent
. Inherits from Event
.
Event properties
This interface also inherits properties from its parent, Event
.
MessageEvent.data
Read only-
The data sent by the message emitter.
MessageEvent.origin
Read only-
A string representing the origin of the message emitter.
MessageEvent.lastEventId
Read only-
A string representing a unique ID for the event.
MessageEvent.source
Read only-
A
MessageEventSource
(which can be a WindowProxy,MessagePort
, orServiceWorker
object) representing the message emitter. MessageEvent.ports
Read only-
An array of
MessagePort
objects representing the ports associated with the channel the message is being sent through (where appropriate, e.g. in channel messaging or when sending a message to a shared worker).
Examples
Suppose a script sends a message to a different browsing context, such as another <iframe>
, using code like this:
const targetFrame = window.top.frames[1];
const targetOrigin = "https://example.org";
const windowMessageButton = document.querySelector("#window-message");
windowMessageButton.addEventListener("click", () => {
targetFrame.postMessage("hello there", targetOrigin);
});
The receiver can listen for the message using addEventListener()
with code like this:
window.addEventListener("message", (event) => {
console.log(`Received message: ${event.data}`);
});
Alternatively the listener could use the onmessage
event handler property:
window.onmessage = (event) => {
console.log(`Received message: ${event.data}`);
};
Specifications
Specification |
---|
HTML Standard # event-message |
HTML Standard # handler-window-onmessage |
Browser compatibility
BCD tables only load in the browser
See also
- Related events:
messageerror
. Window.postMessage()
.