Detailed explanation of JavaScript read-only properties in one article

Javascript is a widely used programming language used to achieve dynamics and interactivity in web applications. In Javascript, a property refers to a characteristic or characteristic of a given object. Object properties can be defined as read-write or read-only. Read-only attributes mean that the attribute value can only be read, but cannot be modified or deleted. In this article, we will introduce the concept of read-only properties in Javascript, their usage, and how to create them.

1. Definition of read-only attributes

Read-only attributes refer to attributes whose value cannot be modified or deleted once created. The read-only property value is a fixed value and cannot be changed by JavaScript code. For example, if a read-only property is a string, its value will always be that string and cannot be changed. Read-only properties are often used to protect code and objects from accidental changes. Read-only properties are often used to prevent errors and undesired side effects.

2. Use of read-only attributes

Read-only attributes can be used in many scenarios, such as the following examples:

1. For some input boxes, they need to be set to only Read to ensure that the content inside the input box is not modified by the user.
2. The attributes of some important data need to be set to read-only to prevent these data from being changed by others, such as passwords, user accounts, etc.
3. For some UI components, they need to be set to read-only to ensure that the values ​​of these components are not accidentally modified.

3. Creation of read-only attributes

Javascript objects can be created in many different ways. If we want to create a read-only property, we need to use the Object.defineProperty() function. This function is used to define a new property on the object, or modify an existing property of the object. This property can be read-only or read-write. Here is the basic syntax for a read-only property:

Object.defineProperty(obj, prop, {
    value: value,
    writable: false,
    configurable: false
});

In this syntax, we first define an object and define a new property on this object. This new property is a read-only property and cannot be modified or deleted. Please note that the value of this property can be specified when the object is created, and the writable and configurable options are provided to set whether the property is writable and configurable. If the configurable option is set to false, the attribute cannot be deleted. If the writable option is set to false, the property becomes read-only.

4. Example of read-only property

The following code example demonstrates how to create a read-only property:

var obj = {};
Object.defineProperty(obj, 'name', {
    value: '张三',
    writable: false,
    configurable: false
});
console.log(obj.name); // “张三”
obj.name = '李四';
console.log(obj.name); //还是 “张三”
delete obj.name;
console.log(obj.name); //还是 “张三”

In this code example, we create an object obj , and creates a read-only property name on this object. We also set the writable and configurable options for this property to ensure it is read-only. Finally, we tried modifying the property and deleting the property. However, both operations were unsuccessful. In the console, we can see that the value of obj.name is always "Zhang San".

Summary:

Read-only attributes are one of the very useful features in Javascript. Read-only attributes can protect objects from being changed incorrectly in certain scenarios, thereby improving the reliability of your code. In this article, we learned about the concept of read-only properties, their usage, and how to create them in Javascript.

The above is the detailed content of Detailed explanation of JavaScript read-only properties in one article. For more information, please follow other related articles on the PHP Chinese website!