node.js: Implementing custom event emitter

By extending EventEmitter class, you can create custom event emitter.

Example

var EventEmitter = require('events').EventEmitter;

class ClockEmitter extends EventEmitter {};

Since ClockEmitter is a sub class of EventEmitter, it inherits all the functionality of EventEmitter class.

You can add listener like below.

myClockEmitter.on("minutesChange", (hour, minutes, seconds) => {

    console.log(`Minute changed: ${hour}:${minutes}:${seconds}`);

});

You can emit the event like below.

myClockEmitter.emit("minutesChange", 12, 46, 23);

Find the below working application.

HelloWorld.js

var EventEmitter = require('events').EventEmitter;

class ClockEmitter extends EventEmitter {};

var myClockEmitter = new ClockEmitter();

myClockEmitter.on("minutesChange", (hour, minutes, seconds) => {
    console.log(`Minute changed: ${hour}:${minutes}:${seconds}`);
});

myClockEmitter.on("hoursChange", (hour, minutes, seconds) => {
    console.log(`Hour changed: ${hour}:${minutes}:${seconds}`);
});

myClockEmitter.emit("minutesChange", 12, 46, 23);
myClockEmitter.emit("hoursChange", 1, 46, 23);

Output

Minute changed: 12:46:23

Hour changed: 1:46:23

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