JS：我正在尝试理解事件发射器与事件侦听器

Question

I am trying to understand the difference between event handlers and event emitters. I understand event listeners and how to attach them, for example, the following:

let element = document.getElementById('test-id');

element.addEventListener('click', handleClick)
})

function handleClick() {
    console.log("is this function considered an event handler?")
}

But even after reading about event emitters and handlers, I don't know exactly how or where they come into play.

Answer 1

you can call the emit() method whenever you need, passing the name of the event and any number of arguments. For example:

const EventEmitter = require( 'events' );
class MyClass extends EventEmitter {
    doSomething() {
        // do something...
        if ( !err )
            this.emit( 'success', result );
        else
            this.emit( 'error', err );
    }
}

You can find the full API documentation of the EventEmitter class here .

Refer here also What is an "event emitter"?

Answer 2

event emitters - code that create event - you write code to create events and then you write handlers for it.

event listeners - event is created by browser eg - http request, click- you write code to handle the events that is listeners.