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node概念笔记之eventemitter

2024-08-11 02:58:55   212人阅读

1、产生事件分发的对象都是eventemitter的实例

2、events模块只提供一个对象events.EventEmitter,核心就是事件触发和事件监听功能的封装

引入方式　　

//引入events模块var events = require(‘events‘);//创建eventEmitter对象var eventEmitter = new events.EventEmitter();

EventEmitter对象如果在实例化时发生错误，会触发error事件，当添加新的监听器时newListener事件触发，移除时removeListener事件被触发

//event.js文件var EventEmitter = require(‘events‘).EventEmitter;var event = new EventEemitter();event.on(‘some_event‘,function(){   console.log(‘some_event 事件触发‘) });setTimeOut(function(){    event.emit(‘some_event‘);},1000)

一秒后触发some_event，然后监听到这个事件的分发

 

支持若干事件监听器，顺序执行，事件参数作为会掉函数的参数传递

var events = require(‘events‘);var emitter = new events.EventEmitter();emitter.on(‘someEvent‘,function(arg1,arg2){   console.log(‘listener1‘,arg1,arg2); });emitter.on(‘someEvent‘,function(arg1,arg2){   console.log(‘listener2‘,arg1,arg2); });emitter.emit(‘someEvent‘,arg1,arg2);

下面是是EventEmitter的属性介绍

1、addListener(event,listener)

2、on(event,listener)//回调函数

3、once,单次事件监听，触发后立即解除

4、removeListener

5、removeAllListeners

6、setMaxListeners

7、listeners返回执行事件的监听器数组

8、emit，按参数执行每个监听器

 

实例

var events = require(‘events‘);var eventEmitter = new events.EventEmitter();//监听器#1var listener1 = function listener1(){  console.log(‘监听器Listener1执行‘)}//监听器#2var listener2 = function listener2(){  console.log(‘监听器Listener2执行‘)}eventEmitter.addListener(‘connect‘,listener1);eventEmitter.addListener(‘connect‘,listener2);var eventListeners = require(‘events‘).EventEmitter.EventEmitterCount(eventEmitter,‘connect‘);console.log(evnetListeners+‘个监听器监听连接事件‘);eventEmitter.emit(‘connect‘);// 移除监绑定的 listener1 函数eventEmitter.removeListener(‘connection‘, listener1);console.log("listener1 不再受监听。");// 触发连接事件eventEmitter.emit(‘connection‘);eventListeners = require(‘events‘).EventEmitter.listenerCount(eventEmitter,‘connection‘);console.log(eventListeners + " 个监听器监听连接事件。");console.log("程序执行完毕。");

 

error事件

继承EventEmitter

 

node概念笔记之eventemitter


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