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异步Promise
(function(w){ function Promise(fn){ return this instanceof Promise ? this.init(fn) : new Promise(fn); } Promise.fulfill = function(m){return m;}; Promise.reject = function(m){throw m;}; Promise.map = { resolve: "onFulfill", reject: "onReject" } //异步自动生成promise并执行 Promise.resolve = function(fn){ var p = new Promise(); setTimeout(function(){ p.resolve(); },0); if(fn) p.callback["onFulfill"] = fn; return p; } Promise.prototype = { init: function(fn){ var that = this; this.state = ‘pending‘; this.callback = { onFulfill: Promise.fulfill, onReject: Promise.reject }; this.dirty = false; this._next = null; setTimeout(function(){ fn && fn.call(that,that.resolve,that.reject); },0) }, then: function(onFulfill,onReject){ return post.call(this,onFulfill,onReject); }, wait: function(mills){ //promise链在wait处被分裂成2段 var p = new Promise(), start = new Date().getTime(); var id = setTimeout(function(){ //传入时间 p.resolve([this.val,new Date().getTime() - start]) },mills); p.cancel = function(){ clearTimeout(id); } return p; }, all: function(){ var p = new Promise(), args; var counter = 0,ret = [];//收集结果，并传给p var v,fn; //传入的函数，执行该函数，将结果保存至ret if(arguments.length > 1){ args = [].slice.apply(arguments) }else if({}.toString.call(arguments[0]) == "[object Array]"){ args = arguments[0]; } for(var i=0,len=args.length;i<len;i++){ if(typeof args[i] == "function"){ args[i] = Promise.resolve(args[i]); } fn = args[i].callback.onFulfill; v = fn.call(args[i]); (function(v){ args[i].then(function(){ ret.push(v); if(--counter <= 0){ ret.length = len; p.resolve(ret); } },function(){ p.reject(); }); })(v) counter++; } return p; } } function post(onFulfill,onReject,onNotify,onComplete){ var p = new Promise(), that = this; if(arguments.length <= 2){ that._next = p; that.callback["onFulfill"] = onFulfill; that.callback["onReject"] = onReject; this.dirty = true; } return p; } function fire(promise,method){ var next = "resolve",val, args = arguments[2]; if(promise.state == "pending"){ try{ this.val = val = promise.callback[Promise.map[method]].apply(promise,args); promise.state = method; }catch(e){ this.val = val = e; next = "reject"; } if(val && isPromise(val)){ val._next = promise._next; }else{ if(promise._next){ fire(promise._next,next,[val]); } } } return promise; } function isPromise(o){ return o && typeof o == "object" && o.then && typeof o.then == "function"; } "reject,resolve".replace(/\w+/g,function(m){ Promise.prototype[m] = function(){ return fire(this,m,arguments); } }) w.Promise = Promise; })(window) function f1(i){console.log("f1",i);return "f1 generate"} function f2(i){console.log("f2",i);return "f2 generate"} function f2e(i){console.log("err:",i)} function f3(){setTimeout(function(){console.log(‘f3‘)},2000);return ‘f3‘} new Promise(function(){ // console.log(this) this.resolve("start:") }).all(f1,f3).then(f2)
实例：
var getJson = function(url){ return new Promise(function(resolve,reject){ var xhr = new XMLHttpRequest(); if(!window.Promise)return; xhr.open(‘get‘,url); xhr.onreadystatechange = function(e){ if(xhr.readyState == 4){ if(xhr.status >= 200 && xhr.status < 300 || xhr.status == 304){ resolve(xhr.responseText); }else{ reject(new Error(‘response error‘)); } } }; xhr.onerror = function(e){ reject(new Error(‘ajax error‘)); } xhr.send(); }); }; var body = document.body; var addHtml = function(html){ if(typeof html != ‘string‘) return; var p = document.createElement(‘p‘); p.textContent = html; body.insertBefore(p,loading); }; var addHead = function(html){ if(typeof html !== ‘string‘) return; var h = document.createElement(‘h2‘); h.textContent = html; body.insertBefore(h,loading); } var log = function(msg){console.log(msg)}; var loading = document.getElementById(‘loading‘);/* getJson(‘../json/head.json‘).then(JSON.parse).then(function(html){ addHead(html.content); Promise.all(html.urls.map(getJson)).then(function(arr){ arr.forEach(function(content){ addHtml(JSON.parse(content).content); }) }).catch(function(e){ log(‘error in loading content: ‘+ e); }) }).catch(function(e){ log(‘error: ‘ + e); }).then(function(){ loading.style.display = ‘none‘; })*/ getJson(‘../json/head.json‘).then(JSON.parse).then(function(html){ addHead(html.content); var promise = Promise.resolve(); html.urls.forEach(function(url,i){ promise = promise.then(function(){ return getJson(url); }).then(JSON.parse).then(function(html){ addHtml(html.content); }).catch(function(e){ log(‘error in loading body: ‘+ e ); }).then(function(){ if(i == html.urls.length-1) loading.style.display = ‘none‘; }) }) })
异步Promise
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