Implement an event emitter

Implement a minimal event emitter

The pub/sub pattern underlies Node's own EventEmitter, DOM events, and most state-management libraries, this is the mechanism behind all of them, in about 15 lines.

Write createEventEmitter() that returns an object with three methods:

• on(event, handler), registers handler to be called whenever event is emitted.
• off(event, handler), removes that specific handler.
• emit(event, ...args), calls every handler registered for event, passing along any extra arguments.

const emitter = createEventEmitter();
emitter.on("greet", (name) => console.log("hello", name));
emitter.emit("greet", "Amit"); // logs "hello Amit"

Multiple handlers can be registered for the same event, and each should fire independently.