Node.js-从EventEmitter继承 [英] Node.js - inheriting from EventEmitter

问题描述

我在许多Node.js库中看到了这种模式:

I see this pattern in quite a few Node.js libraries:

Master.prototype.__proto__ = EventEmitter.prototype;

(来源此处)

有人可以举个例子给我解释一下，为什么这是一种常见的模式，什么时候方便吗?

Can someone please explain to me with an example, why this is such a common pattern and when it's handy?

推荐答案

如该代码上面的注释所述，它将使Master从EventEmitter.prototype继承，因此您可以使用该'class'的实例进行发射和听事件.

As the comment above that code says, it will make Master inherit from EventEmitter.prototype, so you can use instances of that 'class' to emit and listen to events.

例如，您现在可以执行以下操作:

For example you could now do:

masterInstance = new Master();

masterInstance.on('an_event', function () {
  console.log('an event has happened');
});

// trigger the event
masterInstance.emit('an_event');

更新:正如许多用户指出的那样，在Node中执行此操作的标准"方法是使用"util.inherits":

Update: as many users pointed out, the 'standard' way of doing that in Node would be to use 'util.inherits':

var EventEmitter = require('events').EventEmitter;
util.inherits(Master, EventEmitter);

第二次更新:随着ES6类的出现，建议立即扩展EventEmitter类:

2nd Update: with ES6 classes upon us, it is recommended to extend the EventEmitter class now:

const EventEmitter = require('events');

class MyEmitter extends EventEmitter {}

const myEmitter = new MyEmitter();

myEmitter.on('event', () => {
  console.log('an event occurred!');
});

myEmitter.emit('event');

请参见 https://nodejs.org/api/events.html#events_events

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