function deepCopy(p, c) { 
    var c = c || (p instanceof Array?[]:{});  
    for (var i in p) { 

        if(!p.hasOwnProperty(i)){ //只对本身属性和方法进行copy
            continue;  
        }  
  
        if (p[i] && typeof p[i] === 'object') {  //Object or Array except null
            c[i] = (p[i].constructor === Array) ? [] : {};  
            deepCopy(p[i], c[i]);  
        } else {  
            c[i] = p[i];  
        }  
    }  
    return c;  
}

var xm = {
    name:"小明",
    age:18,
    lessons:['数学','语文','英语'],
    brothers:[{
        name:"大明",
        age:19
    },{
        name:"小小明",
        age:17
    }],
    sayHi:function(){
        console.log("hi,我是小明~");
    },
    girlFriends:null
};

var nObj = deepCopy(xm);

console.log(nObj);