//返回新对象，双方互不影响

function clone(obj){

    //alert('clone');

    if(typeof(obj) != 'object') return obj;

    if(obj == null) return obj; //因为typeof(null) == object所以要加上这步

    var newObj = {};

    for(var i in obj){

        newObj[i] = clone(obj[i]);

        //alert('obj['+i+'] '+obj[i]);

    }

    return newObj;

}

function clone2(obj){

    //alert('clone2');

    function F(){}

    F.prototype = obj;

    return new F();

}