深拷贝，浅拷贝

function deepCopy(o){
    return JSON.parse(JSON.stringify(o));
}
var a = {a:1,b:2,c:3};
var b = deepCopy(a);
b.a = 4;
alert(a.a); //1        
alert(b.a); //4

function getType(o){
    return ((_t = typeof(o)) == "object" ? o==null && "null" || Object.prototype.toString.call(o).slice(8,-1):_t).toLowerCase();
}
function extend(destination,source){
    for(var p in source){
        if(getType(source[p])=="array"||getType(source[p])=="object"){
            destination[p]=getType(source[p])=="array"?[]:{};
            arguments.callee(destination[p],source[p]);
        }else{
            destination[p]=source[p];
        }
    }
}
var test={a:"ss",b:[1,2,3],c:{d:"css",e:"cdd"}};
var test1={};
extend(test1,test);
test1.b[0]="change"; //改变test1的c属性对象的d属性
alert(test.b[0]);  //不影响test，返回1
alert(test1.b[0]); //返回change