javascript 各框架的each

 

Object.prototype.each = function()
{
    // 由于HTML DOM不属于JavaScript对象，所以要迭代的话，必须
    // 用下面的方式才能迭代，其中oHtmlDom是你要迭代的HTML DOM对象
    // ({obj:oHtmlDom}).each(function(){var o = this;/*这里省略你要写的代码*/});
    // 这个变量在下面的匿名函数中会用到: _t
    // bNlen 加了标志后控制深度迭代的时候性能大幅度提升
    var _this = this.obj && [this.obj] || this, arg = arguments, _t = this, bDepth, isHtml = false, bNlen, bThis = !!_this;
    // 如果没元素进行迭代，就以一般的对象方式来迭代，然后就返回
    if(!bThis || 0 == arg.length)return this;
    // 如果是String就拆分成数组
    // 你知道为什么要用switch吗，请继续阅读后面的章节
    switch(_this.constructor)
    {
       case String:
       case Number:
       case Boolean:
           _this = String(_this).split("");
           break;
    }
    this.length = _this.length || 0;
    // 这里提供可控制的迭代开始和结束点
    // 支持外面使用bind技术设置内部的迭代开始和结束的下标
    this._eachPos || (this._eachPos = 0);
    this._eachEnd || (this._eachEnd = _this.length);
    // 下面的迭代匿名函数中的this是匿名函数自己的this，
    // 因此这里定义一个匿名函数中能访问的变量，
    // 虽然我们能使用bind来处理，但是会开销bind的时间

    // 上面已经判断，这里就不判断了
    // 支持迭代的时候，允许传入多个function，依次迭代执行
    // 每一个迭代的function执行完所有元素的迭代后才回执行下一迭代器
    switch((bDepth = arg[arg.length - 1]).constructor)
    {
       case Boolean:
           // 如果不是迭代函数而仅仅是标志就移除他
           arg.pop();
           break;
       default :bDepth = false;
    }
    var i = 0;
    // 兼容普通对象的迭代
    if(_t._eachPos == _t._eachEnd)
    {
       if(Array != this.constructor && !this.obj)
       // 原本用i--性能会有提升的，但是这里不能这样
       for(i = 0; i < arg.length; i++)
         for(var k in this)
            arg[i].apply(this, [this[k], k]);
       return this;
    }
    else try{do
    {
        var j = -1, k = _t._eachEnd - _t._eachPos, n = k % 8, oN = n, oCurObj;
        while(j++, 0 < n--)
        {
            bNlen = false;
            oCurObj = _this[j];
            // 兼容深度迭代能选择iframe,frame里的内容
            // 增加bNs标志，表示不对内嵌的窗口进行处理
            if(!_t['bNs'] && !!oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            // 如果元素还可以迭代，并且要求深层迭代则继续迭代
            // 如果深度迭代的是Array，则当前为Array的元素就不处理了
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
        }
        n = (k - oN) / 8;
        while(0 < n--)
        {
            // 由于这里对性能的要求很高，所以采用直接硬编码
            bNlen = false;
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 2
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 3
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 4
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 5
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 6
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 7
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
            // 8
            bNlen = false;
            oCurObj = _this[j];
            if(!_t.bNs && oCurObj['contentWindow'])arg[i].apply(oCurObj, [oCurObj, j]), oCurObj = _A(oCurObj.contentWindow.document.getElementsByTagName("*")),bNlen = true;
            if(bDepth || bNlen)
            {
               arg[i].apply(oCurObj, [oCurObj, j]);
               if(oCurObj['each'])oCurObj.each(arg[i], bDepth);
               // 这里其实可以用_this[j].all的，但是那样会性能能更低
               else if(oCurObj['childNodes'] && 0 < oCurObj.childNodes.length)_A(oCurObj.childNodes).each(arg[i], bDepth);
               else ({obj:oCurObj}).each(arg[i], bDepth);
            }
            else arg[i].apply(oCurObj, [oCurObj, j]);
            j++;
        }
    }while(++i < arg.length)}catch(e){}
  return this;
};

下面是jquery的each函数

 

    each: function( object, callback, args ) {
        var name, i = 0, length = object.length;

        if ( args ) {
            if ( length === undefined ) {
                for ( name in object )
                    if ( callback.apply( object[ name ], args ) === false )
                        break;
            } else
                for ( ; i < length; )
                    if ( callback.apply( object[ i++ ], args ) === false )
                        break;

        // A special, fast, case for the most common use of each
        } else {
            if ( length === undefined ) {
                for ( name in object )
                    if ( callback.call( object[ name ], name, object[ name ] ) === false )
                        break;
            } else
                for ( var value = object[0];
                    i < length && callback.call( value, i, value ) !== false; value = object[++i] ){}
        }

        return object;
    },