How to create custom event listener in node.js (express.js)?

Question

I have a giant function with a lot of nested callbacks. I want to make it cleaner and easier to handle. So, I'm thinking of using custom event listeners

Like, when a function is done, in the callback, instead of putting a chunk of code, it just emits an event, and then the listener will run.

So, how to do that in node.js? I am still looking for a good example to guide me through.

Answer 1

You can set events like this

app.on('event:user_created', callback);

Then you can emit them

app.emit('event:user_created', data);

express.js uses EventEmitter.

Answer 2

The Node.js "events" module and the "EventEmitter" module facilitates communication between objects in Node. The EventEmitter module is at the core of Node's asynchronous event-driven architecture. Here is how you can create custom events and emit them:

const EventEmitter = require('events');
const myEmitter = new EventEmitter();

//Event Listener
const EventListenerFunc = () => {
 console.log('an event occurred!');
}

//Registering the event with the listener
myEmitter.on('eventName', EventListenerFunc);

//Emitting the event 
myEmitter.emit('eventName');