类

class 关键字为语法糖写法，本质是原型链写法。

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  sayName() {
    console.log(this.name);
  }
  sayAge() {
    console.log(this.age);
  }
}

const p = new Person('John', 18);
p.sayName();
p.sayAge();

John
18

function People(name, age) {
  this.name = name;
  this.age = age;
}

People.prototype.sayName = function () {
  console.log(this.name);
};

People.prototype.sayAge = function () {
  console.log(this.age);
};

const q = new People('John', 18);
q.sayName();
q.sayAge();

John
18