'use strict'

class Student {

    constructor(_name,age){

        this.name = _name;

        this.age = age;

    }

    set name(_name){

        this._name = 'aaa'+_name;

    };

    get name(){

        return this._name;

    };

    set age(a){

        this._age = a;

    }

    get age(){

        return this._age;

    }

}
var ss =new Student('yan',19);
new时候先执行constructor,然后发现this.name然后找到了set 后的name这个方法。
console.log(ss);