demo

    <script>        
        var p = {
            name: "chen",
            work: function () {
                console.log("wording...");
            },
            _age: 18,
            get a() {
                return this._age;
            },
            set a(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;
                }
            }
        };
        console.log(p.name);//输出chen
        console.log('p.age: ', p.a); // 18
        console.log('p.age: ', p.a = 20); // 20
        // console.log('p.age: ', p.a = 200); // 抛出错误
        console.log("~~~~~~~~~~~~~~~~~~~~~~");
        let obj = {}
        Object.defineProperty(obj, 'test', {
            get: function () {
                console.log('调用get方法')
            },
            set: function (newVal) {
                console.log('调用set方法,新值为：' + newVal)
            }
        })
        obj.test; // '调用get方法'
        obj.test = '我们都是打工人' // 调用set方法,新值为：我们都是打工人
    </script>