如何声明一个类？类如何继承？

// 声明一个简单的类
class Animal {
  constructor(name) {
    this.name = name;
  }
 
  speak() {
    console.log(`${this.name} makes a sound.`);
  }
}
 
// 继承 Animal 类的子类
class Dog extends Animal {
  constructor(name, breed) {
    super(name); // 调用父类的构造函数
    this.breed = breed;
  }
 
  speak() {
    console.log(`${this.name} barks loudly.`);
  }
}
 
// 创建类的实例并调用方法
const myDog = new Dog('Buddy', 'Golden Retriever');
myDog.speak(); // 输出 "Buddy barks loudly."