MessageChannel
- Node.js course
- Advanced
- Lesson 10/83
- 5 min
Learn inter-worker channels with MessageChannel.
MessageChannel
MessageChannel creates two connected ports: port1 and port2. A message written to one port appears as a "message" event on the other. This lets you set up a direct communication channel between workers.
A typical use: the main thread creates a MessageChannel, transfers port2 to a worker with worker.postMessage(msg, [port2]). Now two workers can talk to each other without going through the parent. This reduces the parent bottleneck when you have many workers.
port1 and port2
When you create a MessageChannel you get port1 and port2. Calling port1.postMessage(data) fires port2.on("message", handler), and vice versa.
Ports are EventEmitters; you listen for on("message"), on("close") and similar events. You may need to call port.start() to activate a port; otherwise messages queue up. When done, close the port with port.close().
Practice Log the type of port1.postMessage
Import the MessageChannel class. Create a new channel. Log typeof port1.postMessage.
Starter code
// Import MessageChannel
// create a channel
// log the type of postMessageSample solution
const { MessageChannel } = require("worker_threads");
const { port1, port2 } = new MessageChannel();
console.log(typeof port1.postMessage);Expected output
function
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does MessageChannel create?
- Tek bir port
- Two connected ports Correct answer
- Three separate channels
- A thread
Explanation: MessageChannel creates two connected ports.
2 Match each piece to its role
| Term | Meaning |
|---|---|
MessageChannel |
Creates two ports |
port1 |
One side |
port2 |
Other side |
port.postMessage |
Sends message |
3 Complete the class name
const { port1, port2 } = new ____()const { port1, port2 } = new MessageChannel()Explanation: new MessageChannel() creates two connected ports.