JavaScript中的类(Class)与继承详解_js ES6+

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  sayHello() {
    console.log(`你好，我是${this.name}，今年${this.age}岁`);
  }
}

const p1 = new Person("小明", 25);
p1.sayHello(); // 输出：你好，我是小明，今年25岁

class MathUtils {
  static add(a, b) {
    return a + b;
  }
}

console.log(MathUtils.add(2, 3)); // 输出：5

// const mu = new MathUtils();
// mu.add(2, 3); // 报错：mu.add is not a function

class Student extends Person {
  constructor(name, age, grade) {
    super(name, age); // 调用父类构造函数
    this.grade = grade;
  }

  study() {
    console.log(`${this.name} 正在学习，年级：${this.grade}`);
  }

  // 重写父类方法
  sayHello() {
    console.log(`我是学生 ${this.name}，${this.age}岁，读${this.grade}年级`);
  }
}

const s1 = new Student("小红", 20, "大三");
s1.sayHello(); // 输出：我是学生 小红，20岁，读大三
s1.study();    // 输出：小红 正在学习，年级：大三

class BankAccount {
  #balance = 0; // 私有字段

  deposit(amount) {
    if (amount > 0) {
      this.#balance += amount;
    }
  }

  getBalance() {
    return this.#balance;
  }
}

const account = new BankAccount();
account.deposit(100);
console.log(account.getBalance()); // 100
// console.log(account.#balance); // 语法错误：无法外部访问

class Counter {
  count = 0; // 公共字段

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