2、利用原型继承和类继承两种方案分别实现：Animal(动物)、Elephant(大象)，其中Animal有名字(name)、年龄(age)、类型(type，如大象或老虎)等属性和toString（返回动物的name、age、type等属性构成的字符串）、cry（不知道怎么叫喊，空方法）等方法，Elephant有noseLength（鼻子长度）属性和sprayWater(喷水)、toString、cry等方法。（17分）

使用原型继承实现：

// 定义 Animal 原型对象
const Animal = {
  init(name, age, type) {
    this.name = name;
    this.age = age;
    this.type = type;
  },
  toString() {
    return `name:${this.name},age:${this.age},type:${this.type}`;
  },
  cry() {},
};

// 定义 Elephant 原型对象
const Elephant = Object.create(Animal);
Elephant.init = function(name, age, noseLength) {
  Animal.init.call(this, name, age, "Elephant");
  this.noseLength = noseLength;
};
Elephant.sprayWater = function() {
  console.log(`${this.name} is spraying water!`);
};
Elephant.toString = function() {
  return `${Animal.toString.call(this)},noseLength:${this.noseLength}`;
};

// 测试代码
const elephant = Object.create(Elephant);
elephant.init("Tom", 5, 2);
console.log(elephant.toString()); // 输出：name:Tom,age:5,type:Elephant,noseLength:2
elephant.sprayWater(); // 输出：Tom is spraying water!

使用类继承实现：

// 定义 Animal 类
class Animal {
  constructor(name, age, type) {
    this.name = name;
    this.age = age;
    this.type = type;
  }

  toString() {
    return `name:${this.name},age:${this.age},type:${this.type}`;
  }

  cry() {}
}

// 定义 Elephant 类
class Elephant extends Animal {
  constructor(name, age, noseLength) {
    super(name, age, "Elephant");
    this.noseLength = noseLength;
  }

  sprayWater() {
    console.log(`${this.name} is spraying water!`);
  }

  toString() {
    return `${super.toString()},noseLength:${this.noseLength}`;
  }
}

// 测试代码
const elephant = new Elephant("Tom", 5, 2);
console.log(elephant.toString()); // 输出：name:Tom,age:5,type:Elephant,noseLength:2
elephant.sprayWater(); // 输出：Tom is spraying water!