js call和apply的 模拟逻辑实现.

   Function.prototype.Apply = function(obj, arr) {
        obj = obj || window;
        obj._tempFunction = this;
        var rv;
        if (!arr) rv = obj._tempFunction();
        else {
            var args = [];
            for (var i = 0, len = arr.length; i < len; i++) args.push('arr[' + i + ']');
            rv = eval("obj._tempFunction(" + args + ")");
        }
        delete obj._temFunction;
        return rv;
    }
    Function.prototype.Call = function() {
        return this.Apply(Array.prototype.shift.Apply(arguments), arguments);
    }
   
    var obj = {};
    function f(a,b,c) {
        alert(this == obj);//看看Apply和Call 是不是把函数内的this 指向了 obj对象
        alert(a + b + c);
    }
    f(1, 2, 3);
    f.Apply(obj, [4, 5, 6]);
    f.Call(obj, 7, 8, 9);