异步编程解决方案之Promise/Deferred

var events = require(‘events‘);
var util = require(‘util‘); 
var EventEmitter = events.EventEmitter;

var Promise = function () {
    EventEmitter.call(this);
}
util.inherits(Promise, EventEmitter);

Promise.prototype.then = function (fulfilledHandler, errorHandler, progressHandler) {
    if (typeof fulfilledHandler === ‘function‘) {
        //利用once（）方法，保证成功回调执行一次
        this.once(‘success‘, fulfilledHandler)
    }
    
    if (typeof errorHandler === ‘function‘) {
        //利用once（）方法，保证异常回调执行一次
        this.once(error, errorHandler)
    }
    
    if (typeof progressHandler === ‘function‘) {
        this.on(‘progress‘, progressHandler)
    }
    return this;
}

var Deferred = function () {
    this.state = ‘unfulfilled‘;
    this.promise = new Promise();
}
Deferred.prototype.resove = function (obj) {
    this.state = ‘fulfilled‘;
    this.promise.emit(‘success‘, obj);
}

Deferred.prototype.error = function (obj) {
    this.state = ‘failed‘;
    this.promise.emit(‘fail‘, obj);
}

Deferred.prototype.progress = function (data) {
    this.promise.emit(‘progress‘, data);
}

res.setEncoding(‘utf8‘)
    res.on(‘data‘, function (chunk){
        console.log(chunk);
    })
    res.on(‘end‘, function (){
        console.log(‘end‘)
    })
    res.on(‘error‘, function (err) {
        console.log(‘err‘);
    })
    res.writeHead(‘200‘, {contentType: ‘text/plain‘});
    res.end(‘练习一下： promise test‘);