js 是否有class 字段

// 定义一个简单的类
class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  greet() {
    console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
  }
}

// 创建类的实例
const person1 = new Person('Alice', 30);
person1.greet(); // 输出: Hello, my name is Alice and I am 30 years old.

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

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

const student1 = new Student('Bob', 15, 10);
student1.greet(); // 输出: Hello, my name is Bob and I am 15 years old.
student1.study(); // 输出: Bob is studying in grade 10.

class MyClass {
  #privateField = 'secret';

  getPrivateField() {
    return this.#privateField;
  }
}

const instance = new MyClass();
console.log(instance.getPrivateField()); // 正确
console.log(instance.#privateField); // 错误: SyntaxError: Private field '#privateField' must be declared in an enclosing class

class Parent {
  constructor(name) {
    this.name = name;
  }
}

class Child extends Parent {
  constructor(name, age) {
    this.age = age; // 错误: this is not defined
    super(name);
  }
}

class Child extends Parent {
  constructor(name, age) {
    super(name);
    this.age = age; // 正确
  }
}