从超类型继承属性的问题

Question

我正在创建一个 Animal 超类型构造函数，该构造函数的方法应该适用于所有“鸟”和“猫”对象。

• 我应该如何添加此原型以确保不会覆盖子类型的原型？
• 我可以在超类型原型中使用子类型原型的变量吗？

示例

function Animal() { }

Animal.prototype = {
  constructor: Animal,
  say: function(sound) {
    console.log(`${sound}`);
  }
};

function Cat(name) {
  this.name=name
 }
function Bird(name) {
  this.name=name
 }
Cat.prototype = {
  constructor:Bird,
  sound:'meow'
}
Bird.prototype = {
  constructor:Bird,
  sound:'Bach Op1 D minor'
}

Cat.prototype = Object.create(Animal.prototype)
Bird.prototype = Object.create(Animal.prototype)
//is this overwriting the prototype already set?
let myCat = new Cat("rupert")
console.log(myCat.name, myCat.say(), Cat.prototype)

Answer 1

您可以使用Object.assign 继承 Animal 的原型，也可以添加自己的字段和方法。另外，您需要使用this.sound 来访问实例本身的属性。

Animal.prototype = {
  constructor: Animal,
  say: function() {
    console.log(`${this.sound}`);
  }
};
//...
Cat.prototype = Object.assign(Object.create(Animal.prototype), {
  constructor:Bird,
  sound:'meow'
});
Bird.prototype = Object.assign(Object.create(Animal.prototype),{
  constructor:Bird,
  sound:'Bach Op1 D minor'
});

演示：

function Animal() { }

Animal.prototype = {
  constructor: Animal,
  say: function() {
    console.log(`${this.sound}`);
  }
};

function Cat(name) {
  this.name=name
 }
function Bird(name) {
  this.name=name
 }
Cat.prototype = Object.assign(Object.create(Animal.prototype), {
  constructor:Bird,
  sound:'meow'
});
Bird.prototype = Object.assign(Object.create(Animal.prototype),{
  constructor:Bird,
  sound:'Bach Op1 D minor'
});
//is this overwriting the prototype already set?
let myCat = new Cat("rupert")
console.log(myCat.name, myCat.say(), Cat.prototype)