js 面向对象 demo

// 定义一个类
class Person {
  // 构造函数，用于初始化对象
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  // 方法：介绍自己
  introduce() {
    return `Hello, my name is ${this.name} and I am ${this.age} years old.`;
  }
}

// 创建对象实例
const person1 = new Person('Alice', 30);
const person2 = new Person('Bob', 25);

// 调用对象的方法
console.log(person1.introduce()); // 输出: Hello, my name is Alice and I am 30 years old.
console.log(person2.introduce()); // 输出: Hello, my name is Bob and I am 25 years old.

class Student extends Person {
  constructor(name, age, grade) {
    super(name, age);
    this.grade = grade;
  }

  study() {
    return `${this.name} is studying in grade ${this.grade}.`;
  }
}

const student1 = new Student('Charlie', 15, 9);
console.log(student1.introduce()); // 输出: Hello, my name is Charlie and I am 15 years old.
console.log(student1.study()); // 输出: Charlie is studying in grade 9.

class Counter {
  #count = 0;

  increment() {
    this.#count++;
  }

  getCount() {
    return this.#count;
  }
}

const counter = new Counter();
counter.increment();
console.log(counter.getCount()); // 输出: 1
console.log(counter.#count); // 报错: SyntaxError: Private field '#count' must be declared in an enclosing class