nodejs的events包

读Vue-hackernews时，在/store/index.js中发现了对events库的引用。想不到在前端代码中还可以引用nodejs的库，这是webpack的功劳吧 ? 还需要再检查一下！另外，看着代码，发现在前端中使用nodejs的库竟然完全不生疏。趁着机会，正好学习一下events库。

引入

//normal
var EventEmitter  = require('events')['EventEmitter'];
//es6
import {EventEmitter} from 'events'
//translated to 
var _events = require('events')
var store = new _events.EventEmitter()

主要API

• The eventEmitter.on() method is used to register listeners, while the eventEmitter.emit() method is used to trigger the event.
• Using the eventEmitter.once() method, it is possible to register a listener that is immediately unregistered after it is called
• As a best practice, developers should always register listeners for the 'error' event

myEmitter.on('error', (err) => {
  console.log('whoops! there was an error');
});

• All EventEmitters emit the event 'newListener' when new listeners are added and 'removeListener' when a listener is removed.

The EventEmitter instance will emit it's own 'newListener'
event before a listener is added to it's internal array of listeners.

• By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individualEventEmitter instances using the emitter.setMaxListeners(n) method