In-depth discussion of the application and usage of set method in JavaScript

When programming in JavaScript, sometimes we need to modify the properties of objects. For safety and standardization, we usually use the set method to set object properties. This article will delve into the application and usage of the set method in JavaScript.

1. What is the set method?

The set method is an accessor in JavaScript that can be used to set the property value of an object. The set method is automatically called when the attribute value is assigned. This method can provide additional control and inspection of the attribute. In addition, the set method is generally used together with the get method to form a complete property accessor.

2. The syntax of the set method

The syntax of the set method is as follows:

set propName(value) {
    // 操作
}

Among them, propName is the attribute name to be set, and value is the attribute value to be set. The operations inside the set method can be any legal JavaScript code.

3. Usage of set method

1. Control attributes

Through the set method, we can control and check the value of the attribute. For example, we can limit the age attribute of an object to no more than 100:

let person = {
    _age: 0,
    set age(value) {
        if (value > 100) {
            console.log("年龄不能大于100！");
            return;
        }
        this._age = value;
    },
    get age() {
        return this._age;
    }
};
person.age = 120; // 输出 "年龄不能大于100！"
person.age = 30; // 设置成功

In the above code, when the age is set to be greater than 100, the set method will return and output "The age cannot be greater than 100!" Prompt information, thus playing the role of attribute value control.

2. Modify attributes

In addition to controlling attribute values, we can also perform some special processing on attributes inside the set method. For example, we can convert a string attribute to uppercase and lowercase:

let person = {
    _name: "",
    set name(value) {
        if (typeof value !== "string") {
            console.log("姓名必须是一个字符串！");
            return;
        }
        this._name = value.toLowerCase();
    },
    get name() {
        return this._name;
    }
};
person.name = "JACK"; // 设置成功，_name属性值为"jack"

In the above code, the set method internally converts the incoming value to lowercase, thus realizing the modification and processing of the attribute. .

3. Set read-only attributes

If we want a certain attribute to be read only and not allowed to be modified, we can use the set method to achieve this. For example:

let person = {
    _age: 18,
    set age(value) {
        console.log("年龄不能被修改！");
    },
    get age() {
        return this._age;
    }
};
person.age = 20; // 输出 "年龄不能被修改！"
console.log(person.age); // 输出 18

In the above code, when the age attribute of the person object is called for assignment, the set method will output the prompt message "Age cannot be modified!", thereby setting the read-only attribute. .

4. Notes on the set method

1. The properties of an object can be set with both get and set methods at the same time, or only one of them can be set.
2. The set method is generally used together with the get method to form a complete attribute accessor.
3. If only the set method is set and the get method is not set, undefined will be returned when reading the property.
4. Some additional operations and controls can be performed inside the set method, such as checking and modifying attribute values.
5. The set method can be used to implement read-only attributes, as well as access control and processing of attributes.

5. Conclusion

Through the above introduction, we understand the usage and application of the set method in JavaScript. The set method can be used to control the setting of attribute values, modify attributes, set read-only attributes, etc. In actual programming, reasonable use of the set method can improve the readability, robustness and security of the code. Therefore, mastering the application and usage of the set method is very helpful for improving JavaScript programming skills.

The above is the detailed content of In-depth discussion of the application and usage of set method in JavaScript. For more information, please follow other related articles on the PHP Chinese website!