基础篇
        难度 ★
        
        //浅拷贝
        请写出下列代码的输出结果,为什么？

        //1.
        var a = 2 ;
        var a_copy = a ;
        a_copy  = 3;
        console.log(a);//？

        //2.数组1
        var arr = [1,2,3,4];
        var arr_copy = arr ;
        arr_copy.push(5);
        console.log(arr);//？
        //3.数组2
        var arr = [1,2,3,4];
        var arr_copy = arr ;
        arr_copy = [1,2,3,4,5];
        console.log(arr);//？
        console.log(arr_copy);//？

        //4.对象1
        var obj = {
            name:'sunshine',
            age:18
        };
        var obj_copy = obj ;
        obj_copy.name = '过客';
        console.log(obj.name);//？

        //5.对象2
        var obj = {
            name:'sunshine',
            age:18
        };
        var obj_copy = obj ;
        obj_copy = {
            name:'过客',
            age:18
        };
        console.log(obj.name);//？
        console.log(obj_copy.name);//？