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上篇：Javascript 異步編程
好像有這么一句名言——"每一個(gè)優(yōu)雅的接口，背后都有一個(gè)齷齪的實(shí)現(xiàn)"。最明顯的例子，jQuery。之所以弄得這么復(fù)雜，因?yàn)樗緛?lái)就是那復(fù)雜。雖然有些實(shí)現(xiàn)相對(duì)簡(jiǎn)明些，那是它們的兼容程度去不了那個(gè)地步。當(dāng)然，世上總有例外，比如mootools，但暴露到我們眼前的接口，又不知到底是那個(gè)父類的東西，結(jié)構(gòu)清晰但不明撩。我之所以說(shuō)這樣的話，因?yàn)楫惒搅嘘?duì)真的很復(fù)雜，但我會(huì)盡可能讓API簡(jiǎn)單易用。無(wú)new實(shí)例化，不區(qū)分實(shí)例與類方法，鏈?zhǔn)剑葧r(shí)髦的東西都用上。下面先奉上源碼：
;(function(){
var dom = this.dom = this.dom || {
mix : function(target, source ,override) {
var i, ride = (override === void 0) || override;
for (i in source) {
if (ride || !(i in target)) {
target[i] = source[i];
}
}
return target;
}
}
//////////////////////////////////////////////////////////////////////
//=======================異步列隊(duì)模塊===================================
var Deferred = dom.Deferred = function (fn) {
return this instanceof Deferred ? this.init(fn) : new Deferred(fn)
}
var A_slice = Array.prototype.slice;
dom.mix(Deferred, {
get:function(obj){//確保this為Deferred實(shí)例
return obj instanceof Deferred ? obj : new Deferred
},
ok : function (r) {//傳遞器
return r
},
ng : function (e) {//傳遞器
throw e
}
});
Deferred.prototype = {
init:function(fn){//初始化,建立兩個(gè)列隊(duì)
this._firing = [];
this._fired = [];
if(typeof fn === "function")
return this.then(fn)
return this;
},
_add:function(okng,fn){
var obj = {
ok:Deferred.ok,
ng:Deferred.ng,
arr:[]
}
if(typeof fn === "function")
obj[okng] = fn;
this._firing.push(obj);
return this;
},
then:function(fn){//_add的包裝方法1,用于添加正向回調(diào)
return Deferred.get(this)._add("ok",fn)
},
once:function(fn){//_add的包裝方法2,用于添加負(fù)向回調(diào)
return Deferred.get(this)._add("ng",fn)
},
wait:function(timeout){
var self = Deferred.get(this);
self._firing.push(~~timeout)
return self
},
_fire:function(okng,args,result){
var type = "ok",
obj = this._firing.shift();
if(obj){
this._fired.push(obj);//把執(zhí)行過(guò)的回調(diào)函數(shù)包,從一個(gè)列隊(duì)倒入另一個(gè)列隊(duì)
var self = this;
if(typeof obj === "number"){//如果是延時(shí)操作
var timeoutID = setTimeout(function(){
self._fire(okng,self.before(args,result))
},obj)
this.onabort = function(){
clearTimeout(timeoutID );
}
}else if(obj.arr.length){//如果是并行操作
var i = 0, d;
while(d = obj.arr[i++]){
d.fire(args)
}
}else{//如果是串行操作
try{//
result = obj[okng].apply(this,args);
}catch(e){
type = "ng";
result = e;
}
this._fire(type,this.before(args,result))
}
}else{//隊(duì)列執(zhí)行完畢,還原
(this.after || Deferred.ok)(result);
this._firing = this._fired;
this._fired = [];
}
return this;
},
fire:function(){//執(zhí)行正向列隊(duì)
return this._fire("ok",this.before(arguments));
},
error:function(){//執(zhí)行負(fù)向列隊(duì)
return this._fire("ng",this.before(arguments));
},
abort:function(){//中止列隊(duì)
(this.onabort || Deferred.ok)();
return this;
},
//每次執(zhí)行用戶回調(diào)函數(shù)前都執(zhí)行此函數(shù),返回一個(gè)數(shù)組
before:function(args,result){
return result ? result instanceof Array ? result : [result] : A_slice.call(args)
},
//并行操作,并把所有的子線程的結(jié)果作為主線程的下一個(gè)操作的參數(shù)
paiallel : function (fns) {
var self = Deferred.get(this),
obj = {
ok:Deferred.ok,
ng:Deferred.ng,
arr:[]
},
count = 0,
values = {}
for(var key in fns){//參數(shù)可以是一個(gè)對(duì)象或數(shù)組
if(fns.hasOwnProperty(key)){
(function(key,fn){
if (typeof fn == "function")
fn = Deferred(fn);
fn.then(function(value){
values[key] = value;
if(--count <= 0){
if(fns instanceof Array){//如果是數(shù)組強(qiáng)制轉(zhuǎn)換為數(shù)組
values.length = fns.length;
values = A_slice.call(values)
}
self._fire("ok",[values])
}
}).once(function(e){
self._fire("ng",[e])
});
obj.arr.push(fn);
count++
})(key,fns[key])
}
}
self.onabort = function(){
var i = 0, d;
while(d = obj.arr[i++]){
d.abort();
}
}
self._firing.push(obj);
return self
},
//處理相近的迭代操作
loop : function (obj, fn, result) {
obj = {
begin : obj.begin || 0,
end : (typeof obj.end == "number") ? obj.end : obj - 1,
step : obj.step || 1,
last : false,
prev : null
}
var step = obj.step,
_loop = function(i,obj){
if (i <= obj.end) {
if ((i + step) > obj.end) {
obj.last = true;
obj.step = obj.end - i + 1;
}
obj.prev = result;
result = fn.call(obj,i);
Deferred.get(result).then(_loop).fire(i+step,obj);
}else{
return result;
}
}
return (obj.begin <= obj.end) ? Deferred.get(this).then(_loop).fire(obj.begin,obj) : null;
}
}
//將原型方法轉(zhuǎn)換為類方法
"loop wait then once paiallel".replace(//w+/g, function(method){
Deferred[method] = Deferred.prototype[method]
});
})();
it知識(shí)庫(kù)：javascript 異步編程2，轉(zhuǎn)載需保留來(lái)源！
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