Lesson 24 — Pub/sub with topics

Messages by topic

A message broker sits between parts of a system. Publishers send a message to a named topic; subscribers listen to the topics they care about. Neither side knows the other exists. Tools like Redis Pub/Sub, RabbitMQ and Kafka work this way.

b.sub("news", (m) => console.log(m));
b.pub("news", "hello");

Note: this playground runs JavaScript in your browser, not in real Node, so Node-only tools (like fs or http) are not available. The exercise is a small plain-JS simulation of the Node idea.

Why it matters: decoupled services can be added or removed without changing each other.