Nodejs - this.on 不是 function 事件发射器 object inheritance

Question

I'm learning how to use event emitter and inheritance in nodejs. I get the error:

TypeError: this.on is not a function

My code:

const EventEmitter = require('events')

const Emitter = function () {
    EventEmitter.call(this)

    this.on('event',value => {
        console.log('Event emitted',value)
    })
}

const myEmitter = new Emitter()

What I'm doing wrong?

Answer 1

With above code you're not actually inheriting from EventEmitter . I'd just use an actual class that extends it:

const EventEmitter = require('events')

class Emitter extends EventEmitter {
    constructor() {
        super();
        this.on('event', value => {
            console.log('Event emitted', value)
        });
    }
}

const myEmitter = new Emitter();
myEmitter.emit('event', 'hello'); // logs 'Event emitted hello' to the console.