使用原型链

function Animal(legsNumber) {
  this.legsNumber = legsNumber;
}
Animal.prototype.kind = "动物";

function Dog(name) {
  this.name = name;
  Animal.call(this, 4); //构造函数，自身属性
}

Dog.prototype._proto_ = Animal.prototype; //通用属性    但是不是js所推荐的

Dog.prototype.kind = "狗";
Dog.prototype.say = function () {
  console.log(`汪汪汪~ 我是${this.name}，我有${this.legsNumber}条腿。`);
};

Dog.prototype._proto_ = Animal.prototype;  //可以被以下几句替换

const f = function () {};    
f.prototype = Animal.prototype;
Dog.prototype = new f();

使用Class

class Animal {
  constructor(legsNumbers) {
    this.legsNumbers = legsNumbers;
  }
  run() {}
}

class Dog extends Animal {
  constructor(name) {
    super(4);
    this.name = name;
  }
  say() {
    console.log("只因你太美");
  }
}