The Channel Messaging API is a great way to send 1-to-1 messages from a window to an iframe, from a window to a Web Worker, and so on.

The BroadcastChannel API can be used to send 1-to-many messages, communicating to multiple entities at the same time.

You start by initializing a BroadcastChannel object:

const channel = new BroadcastChannel('thechannel')

To send a message on the channel you use the postMessage() method:

channel.postMessage('Hey!')

A message can be any of those supported values:

• All primitive types, excluding symbols
• Arrays
• Object literals
• String, Date, RegExp objects
• Blob, File, FileList objects
• ArrayBuffer, ArrayBufferView objects
• FormData objects
• ImageData objects
• Map and Set objects

To receive messages from the channel, listen to the message event:

channel.onmessage = (event) => {
  console.log('Received', event.data)
}

This event is fired for all listeners, except the one that is sending the message.

You can close the channel using:

channel.close()

Lessons in this unit:

0:	Introduction
1:	Web Workers
2:	▶︎ BroadcastChannel API
3:	Channel Messaging API
4:	requestAnimationFrame