MessageEvent: MessageEvent() constructor

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since August 2016.

Note: This feature is available in Web Workers.

The MessageEvent() constructor creates a new MessageEvent object.

Syntax

js
new MessageEvent(type)
new MessageEvent(type, options)

Parameters

type

A string with the name of the event. It is case-sensitive and browsers always set it to message.

options Optional

An object that, in addition of the properties defined in Event(), can have the following properties:

data Optional

The data you want contained in the MessageEvent. This can be of any data type, and will default to null if not specified.

origin Optional

A string representing the origin of the message emitter. This defaults to an empty string ('') if not specified.

lastEventId Optional

A string representing a unique ID for the event. This defaults to an empty string ("") if not specified.

source Optional

A MessageEventSource (which can be a Window, a MessagePort, or a ServiceWorker object) representing the message emitter. This defaults to null if not set.

ports Optional

An array of MessagePort objects containing all MessagePort objects sent with the message, in order. This defaults to an empty array ([]) if not specified.

Return value

A new MessageEvent object.

Examples

js
const myMessage = new MessageEvent("message", {
  data: "hello",
});

Specifications

Specification

HTML
# the-messageevent-interface:dom-event-constructor

Browser compatibility

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This page was last modified on Oct 29, 2024 by MDN contributors.

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