js不申明变量，自己用就叫动态？无语

Question

<script>var life = {};
    for(life.age = 1; life.age <= 3; life.age++)//自己用就叫动态？无语
    {
        switch(life.age)
        {
            case 1: life.body = "cell of";
                    life.say = function(){alert(this.age+this.body)};
                    break;
            case 2: life.tail = "tail";
                    life.gill = "sai";
                    life.body = "kedou";
                    life.say = function(){alert(this.age+this.body+"-"+this.tail+","+this.gill)};
                    break;
            case 3: delete life.tail;
                    delete life.gill;
                    life.legs = "four leg";
                    life.lung = "lung";
                    life.body = "frog";
                    life.say = function(){alert(this.age+this.body+"-"+this.legs+","+this.lung)};
                    break;
        };
        life.say();
    }; </script>
 

Answer 1

js 算是"弱语言"  即 不需要编译是解释执行。变量不需要显示声明