Object的方法

面向对象

    function Cat(n, c) {
        this.name = n;
        this.color = c;
        this.trait = function () {
            alert('卖萌~');
        };

    };

    Cat.prototype.skill = function () {
        alert('抓老鼠');
    };

    Cat.prototype.abc = 123;

    function Dog(f,n, c) {//子类
        this.food = f;
        Cat.call(this,n,c);

    };

    // Dog.prototype = Object.create(Cat.prototype); ??

    var dog1 = new Dog('aa','bb','cc');
    console.log(dog1.name); //结果:  bb
    dog1.trait(); // 结果: 卖萌

    //面向委托

      var  Cat = {
          init: function (n,c){
              this.name = n;
              this.color= c;
          },
          train: function(){
              alert('卖萌~');
          },
          skill: function(){
              alert('抓老鼠');
          }

      }

      var Dog = Object .create(Cat);
        Dog.setArr = function (f,n,c){
            this.init(n,c)
            this.food= f;
        };


      var dog1 = Object.create(Dog);
      dog1.setArr('aa','bb','cc');
      console.log(dog1.name);

      dog1.skill();


    var obj1 = {a:1, b:2};
    var obj2 = {
        name:'xm',
        age:18,
        say: function(){
            alert('xxxx');
        }
    }

      obj1.c = 3; //设置属性  -> set()
      obj1.a = 4;//修改属性   ->set()
     console.log(obj1.b); //访问属性  -> get()

     Object.defineProperty(obj1,'a',{
         // 是否可配置(删除,枚举,读写);
         configurable:true,
         //是否可枚举(for in  遍历)
         enumerable: true,
         //是否可写
         writable: true,
         //属性值
         value: 5
     });
     console.log(obj1.a) // 结果:  5

     delete obj1.a;

    for(var key in obj1){
        console.log(key);
    }

显示声明与隐式声明变量的区别?