对象中 set 与get 的用法

<script type="text/javascript">
        var p = {
            name:"chen",
            work:function() {
                console.log("wording...");
            },
            _age:18,
            get age(){
                return this._age;
            },
            set age(val) {
                if (val<0 || val> 100) {//如果年龄大于100就抛出错误
                    throw new Error("invalid value")
                }else{
                    this._age = val+'岁了';
                }
            }
        };
        p.age = 20
        console.log(p.age);//输出chen
    </script>