Explore how to create read-only properties in JavaScript

In JavaScript, we often encounter situations where we need to set read-only attributes. The read-only attribute means that the attribute can only be read and cannot be modified, which plays an important role in many situations. In this article, we will explore how to create read-only properties in JavaScript, as well as the uses and applicable scenarios of read-only properties.

1. How to create a read-only property

In JavaScript, there are two ways to create a read-only property: one is to use the Object.defineProperty() method, the other is The first is to use the getter method introduced in ES6.

(1) Object.defineProperty() method

The way to create a read-only property using the Object.defineProperty() method is as follows:

let obj = {};

Object.defineProperty(obj, 'readOnlyProp', {
  value: 'This property is read only',
  writable: false,
  enumerable: true,
  configurable: false
});

console.log(obj.readOnlyProp); // 输出：This property is read only
obj.readOnlyProp = 'new value'; // 尝试修改只读属性
console.log(obj.readOnlyProp); // 输出：This property is read only

In the above code, we use Object The .defineProperty() method defines a read-only property readOnlyProp. Among them, the first parameter is the object to which the attribute is to be added, the second parameter is the name of the attribute, and the third parameter is a configuration object used to define the characteristics of the attribute. In this configuration object, we set writable to false, which means that the property is not writable, and configurable is set to false, which means that the property is not allowed to be deleted or reconfigured.

(2) ES6 getter method

The getter method introduced in ES6 can define read-only properties through the get keyword. The sample code is as follows:

let obj = {
  get readOnlyProp() {
    return 'This property is read only';
  }
};

console.log(obj.readOnlyProp); // 输出：This property is read only
obj.readOnlyProp = 'new value'; // 尝试修改只读属性
console.log(obj.readOnlyProp); // 输出：This property is read only

In the above code, We define a read-only property readOnlyProp through the get keyword. At this time, when obj.readOnlyProp is called, the getter method of the property will be automatically called and a specific value will be returned. Since there is no corresponding setter method defined, this property is not allowed to be modified.

2. The uses and applicable scenarios of read-only attributes

The usage scenarios of read-only attributes are relatively wide. Let’s look at some typical situations below.

(1) Protect the properties of the object

By defining read-only properties, we can protect the properties of the object to prevent them from being modified unnecessarily. This is particularly important in situations where program security needs to be protected. For example, in a multi-person collaboration program, we need to ensure that certain attributes cannot be modified by other users to ensure the correctness and stability of the program.

(2) Set the default value

The read-only attribute can also be used to set the default value. For example, in our code, there may be some indispensable values, and if these values ​​are modified, the entire program will crash. At this point, we can use read-only attributes to set these values ​​and ensure that they will not be modified, thereby ensuring the stability of the program.

(3) Optimize code performance

Read-only attributes can also be used to optimize code performance. Since read-only properties are not allowed to be modified, no additional checks are required when using them: if the property has been modified, appropriate processing is required, otherwise nothing needs to be done. This can greatly reduce the running time of the code and improve the performance of the program.

In short, read-only attributes are a very commonly used feature in JavaScript. It can be used to protect object attributes, set default values, and optimize code performance. By using the read-only attribute properly, we can make the program more secure, stable and efficient.

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