JavaScript 私有字段装饰器集成：增强封装

            class MyClass {
  #privateField = 'secret';

  constructor(initialValue) {
    this.#privateField = initialValue;
  }

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

const instance = new MyClass('initial');
console.log(instance.getPrivateFieldValue()); // Output: initial
// console.log(instance.#privateField); // Error: Private field '#privateField' must be declared in an enclosing class

            

              
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            function logAccess(target, context) {
  const privateKey = context.name;
  return function(initialValue) {
    return {
      get() {
        console.log(`Accessing private field: ${privateKey.description}`);
        return initialValue;
      },
      set(newValue) {
        console.log(`Setting private field: ${privateKey.description} to ${newValue}`);
        initialValue = newValue;
      },
      init(initialValue) {
        console.log("Initializing private field: " + privateKey.description)
        return initialValue
      }
    };
  }
}

class MyClass {
  @logAccess
  #privateField = 'secret';

  constructor(initialValue) {
    this.#privateField = initialValue;
  }

  getPrivateFieldValue() {
    return this.#privateField;
  }

  setPrivateFieldValue(newValue) {
    this.#privateField = newValue;
  }
}

const instance = new MyClass('initial');
console.log(instance.getPrivateFieldValue()); // Output: Accessing private field: #privateField
                                         //         initial
instance.setPrivateFieldValue('updated'); // Output: Setting private field: #privateField to updated

            

              
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            function validate(validator) {
  return function (target, context) {
    const privateKey = context.name;
    return function(initialValue) {
      return {
        set(newValue) {
          if (!validator(newValue)) {
            throw new Error(`Invalid value for private field ${privateKey.description}`);
          }
          initialValue = newValue;
        },
        init(initialValue) {
          if (!validator(initialValue)) {
            throw new Error(`Invalid initial value for private field ${privateKey.description}`);
          }
          return initialValue;
        },
        get() {
          return initialValue;
        }
      };
    };
  };
}

function isString(value) {
  return typeof value === 'string';
}

class MyClass {
  @validate(isString)
  #name = '';

  constructor(name) {
    this.#name = name;
  }

  getName() {
    return this.#name;
  }
}

try {
  const instance = new MyClass(123); // This will throw an error
} catch (e) {
  console.error(e.message);
}

const instance2 = new MyClass("Valid Name");
console.log(instance2.getName());


            

              
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            function readOnly(target, context) {
  const privateKey = context.name;
  return function(initialValue) {
    return {
      set(newValue) {
        throw new Error(`Cannot modify read-only private field: ${privateKey.description}`);
      },
      init(initialValue) {
        return initialValue;
      },
      get() {
        return initialValue;
      }
    };
  };
}

class MyClass {
  @readOnly
  #id = Math.random();

  getId() {
    return this.#id;
  }

  //Attempting to set #id here or anywhere else would throw an error
}

const instance = new MyClass();
console.log(instance.getId());
//instance.#id = 5; //This will cause an error

            

              
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