SOURCE

// new 通过构造函数返回一个对象
var _new = function(){
    var obj = new Object();
    Constructor = [].shift.call(arguments);
    obj._proto_ = Constructor.prototype;
    var ret = Constructor.apply(obj, arguments);
    return typeof ret === 'object' ? ret : obj;
} 




// call 指定this的值并给某个函数赋参数值进行调用

Function.prototype.call2 = function (context){
    // this设置默认值为window
    var context = context || window;
    context.fn = this;

    var args = [];
    for (var i=1, len=arguments.length; i<len; i++){
        args.push('arguments['+i+']');
    }
    var result = eval('context.fn('+args+')');
    //防止函数有返回值，导致提前结束
    delete context.fn;

    return result;
}

var foo = {
    value: 1
};

function bar(name,age){
    console.log(name);
    console.log(age);
    console.log(this.value);
}

bar.call2(foo,'DG',12);