js symbol 私有变量

const privateField = Symbol('privateField');

class MyClass {
  constructor() {
    this[privateField] = 'This is a private field';
  }

  getPrivateField() {
    return this[privateField];
  }
}

const instance = new MyClass();
console.log(instance.getPrivateField()); // 输出: This is a private field
console.log(instance[privateField]); // 直接访问Symbol属性会报错，除非有相应的getter/setter

const privateData = new WeakMap();

class MyClass {
  constructor() {
    privateData.set(this, { privateField: 'This is a private field' });
  }

  getPrivateField() {
    return privateData.get(this).privateField;
  }
}

const instance = new MyClass();
console.log(instance.getPrivateField()); // 输出: This is a private field
console.log(privateData.get(instance)); // 只有通过WeakMap才能访问到私有数据