var EventEmitter = require('events').EventEmitter; var http = require('http'); var util = require('util'); // 定义promise对象 var Promise = function(){ // 实现继承事件类 EventEmitter.call(this); } // 继承事件通用方法 util.inherits(Promise,EventEmitter); // then 方法为promise/A 规范中的方法 Promise.prototype.then = function(successHandler,errorHandler,progressHandler){ if (typeof successHandler == 'function'){ this.once('success',successHandler); } if (typeof errorHandler === 'function'){ this.once('error',errorHandler); } if (typeof progressHandler === 'function'){ this.on('process',progressHandler); } return this; }

// 定义延迟对象 // 包含一个状态和一个promise对象 var Deferred = function(){ this.state = 'unfulfilled'; this.promise = new Promise(); } Deferred.prototype.resolve = function(obj){ this.state = 'fulfilled'; this.promise.emit('success',obj); } Deferred.prototype.reject = function(err){ this.state = 'Failed'; this.promise.emit('error',err); } Deferred.prototype.progress = function(data){ this.promise.emit('process',data); }

// 利用一个http请求来运用上面定义的promise/deferred

var client = function(){ var options = { hostname:'www.baidu.com', port:80, path:'/', method: 'get' }; var deferred = new Deferred(); var req = http.request(options,function(res){ res.setEncoding('utf-8'); var data = ''; res.on('data',function(chunk){ data += chunk; deferred.progress(chunk); }); res.on('end',function(){ deferred.resolve(data); }); }); req.on('error',function(err){ deferred.reject(err); }) req.end(); return deferred.promise; } client().then(function(data){ console.log('请求完成',data); },function(err){ console.log('访问错误',err); },function(chunk){ console.log('正在读取',chunk); });