Hiding of javascript classes

JavaScript is a commonly used scripting language that is often used in web development and can work together with HTML and CSS to achieve front-end interaction and dynamic effects. In JavaScript, classes are a commonly used object-oriented programming pattern that can achieve code reuse and encapsulation, and group code into related functional modules. Class hiding is one of the features, which can hide certain properties and methods of a class to prevent external access and changes, improving the security and stability of the code.

1. Classes and hidden concepts of classes

A class is an object-oriented programming model. It is an abstract concept that can abstract things in the real world into classes. Properties and methods to achieve code reuse and encapsulation. In JavaScript, a class is a special object that can be defined and created using the keyword class.

Class hiding is to hide certain attributes and methods of the class to prevent external access and changes, and improve the security and stability of the code. In JavaScript, this can be achieved in the following ways:

1. Use the let and const keywords to define the properties and methods of a class and limit them to the scope of the class to prevent external access and changes.
2. Use symbol type attribute names to define class attributes and methods, which can be named as unique identifiers to prevent external access and changes.
3. Use closures to hide the attributes and methods of the class and define them inside the function so that they cannot be directly accessed from the outside.

2. Hidden implementation of classes

1. Use let and const keywords

In JavaScript, let and const keywords Can be used to declare variables and constants, which have block-level scope and can only be accessed within the code block in which they are defined. In a class, you can use the let and const keywords to define properties and methods, limiting them to the scope of the class to prevent external access and changes.

The sample code is as follows:

class Person {
  constructor(name, age) {
    let _name = name;
    const _age = age;

    this.getName = function () {
      return _name;
    }

    this.getAge = function () {
      return _age;
    }
  }
}

In this example, the attributes _name and _age in the class Person are defined using the let and const keywords, and they can only be used in the constructor access. In the constructor, two methods, getName and getAge, are defined to obtain the values ​​of _name and _age. Since _name and _age are limited to the scope of the class, the outside world cannot directly access and change their values, thus hiding the attributes and methods of the class.

2. Use symbol type attribute names

In JavaScript, the symbol type is a unique identifier that can be used to define the attributes and methods of a class to prevent external access and change. Through attribute names of symbol type, attributes and methods can be named as unique identifiers, which can be used within the scope of the class and cannot be directly accessed and changed elsewhere.

The sample code is as follows:

const _name = Symbol('name');
const _age = Symbol('age');

class Person {
  constructor(name, age) {
    this[_name] = name;
    this[_age] = age;
  }

  getName() {
    return this[_name];
  }

  getAge() {
    return this[_age];
  }
}

In this example, the two attribute names _name and _age are defined using Symbol('name') and Symbol('age') respectively. In the constructor, use this[_name] and this[_age] to save the values ​​of the name and age attributes. In the getName and getAge methods, use this[_name] and this[_age] to get the value of the attribute. Since _name and _age are unique identifiers, the outside world cannot directly access and change their values, thus hiding the attributes and methods of the class.

3. Using closures

In JavaScript, closures can be used to privatize variables. By defining variables and methods inside the function, the access rights of variables and methods are controlled inside the function to prevent external access and changes. In a class, you can use closures to hide class properties and methods by defining them inside functions.

The sample code is as follows:

class Person {
  constructor(name, age) {
    let _name = name;
    let _age = age;

    function getName() {
      return _name;
    }

    function getAge() {
      return _age;
    }

    this.getName = getName;
    this.getAge = getAge;
  }
}

In this example, the _name and _age attributes and the getName and getAge methods are defined inside the constructor. Inside the getName and getAge methods, the _name and _age properties are accessed. Outside the constructor, access the getName and getAge methods through this.getName and this.getAge methods. Since _name and _age are defined inside the constructor, their values ​​cannot be directly accessed and changed by the outside world, thus hiding the attributes and methods of the class.

3. The role of class hiding

The hiding of classes can improve the security and stability of the code, prevent external access and changes to the properties and methods of the class, and avoid unexpected situations.

1. Security

The hiding of classes can protect the data of the class, prevent external access and changes, ensure the security of the data, and avoid data leakage.

2. Stability

The hiding of the class can maintain the stability of the class, prevent external access and change the internal implementation details of the class, avoid unnecessary interference and impact, and ensure Code stability.

3. Maintainability

Hiding classes can improve the maintainability of the code, hide the implementation details of the class, reduce the complexity of the code, and improve the readability and readability of the code. Maintainability.

4. Summary

Class is a commonly used object-oriented programming model in JavaScript. It can achieve code reuse and encapsulation, and group code into related functional modules. Class hiding is one of the features, which can hide certain attributes and methods of a class to prevent external access and changes, improving the security and stability of the code. In JavaScript, you can use the let and const keywords, symbol type attribute names and closures to hide classes, and choose different methods according to different scenarios.

Hiding classes can improve the security and stability of the code, protect the data of the class, reduce the complexity of the code, and improve the readability and maintainability of the code. In actual development, an appropriate implementation method should be selected based on the actual situation to hide classes and ensure the quality and stability of the code.

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