探索node之事件循环的实现

// 引入events模块
let events = require('events');
//创建eventEmitter对象
let eventEmitter = new events.EventEmitter();

//绑定事件以及事件处理程序
eventEmitter.on('eventName',eventHandler);

//通过程序触发事件
eventEmitter.emit('eventName')

//引入events模块
let events = require('events');

//创建eventEmitter对象
let eventEmitter = new events.EventEmitter();

//创建事件处理程序
let connectHandle = function connected() {
 console.log('连接成功');
 //触发data_received事件
 eventEmitter.emit('data_received')
}

//绑定connection事件处理程序
eventEmitter.on('connection', connectHandle);

//使用匿名函数绑定data_received事件
eventEmitter.on('data_received', function () {
 console.log('数据接收成功');
})

//触发connecttion事件
eventEmitter.emit('connection');
console.log('程序执行完毕');


// 执行结果：
// 连接成功
// 数据接收成功
// 程序执行完毕

var EventEmitter = require('events').EventEmitter; 
var event = new EventEmitter(); 
event.on('some_event', function() { 
  console.log('some_event 事件触发'); 
}); 
setTimeout(function() { 
  event.emit('some_event'); 
}, 1000); 

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 参数', 'arg2 参数'); 
//输出：
// listener1 arg1 参数 arg2 参数
// listener2 arg1 参数 arg2 参数

/*
 * @Author: angula
 * @Date: 2020-09-21 22:29:18
 * @LastEditTime: 2020-09-22 11:27:56
 * @FilePath: \JS\Github-前端知识总结仓库\studySummary\Node.js学习笔记\事件循环\index2.js
 */
let events = require('events');
let eventEmitter = new events.EventEmitter();

// 监听器1
let listener1 = function listener1() {
 console.log('监听器listener1启动。。。');
}

// 监听器2
let listener2 = function listener2() {
 console.log('监听器listener2启动。。。');
}

// 绑定connection事件，处理函数为listener1
eventEmitter.addListener('connection', listener1);
// 绑定connection事件，处理函数为listener2
eventEmitter.on('connection', listener2);


//类，返回监听器的数量

let eventListeners = eventEmitter.listenerCount('connection');
console.log(eventListeners + '个监听器监听连接事件。');


//处理connection事件
eventEmitter.emit('connection');

// 移除绑定的listener1
eventEmitter.removeListener('connection', listener1);
console.log('listener1不再受监听');

//触发连接事件
eventEmitter.emit('connection');

eventListeners = eventEmitter.listenerCount('connection');
console.log(eventListeners + '个监听器连接事件');

console.log('程序执行完毕');