Public Instance Setters in JavaScript Classes

In this article, we will learn about public instance setters in JavaScript classes. Public instance setters are methods that allow us to set the value of a public instance property of a class. Public instance properties are properties that belong to each instance of a class, and can be accessed and modified by anyone.

Why Use Public Instance Setters?

Public instance setters are useful for several reasons:

• They can provide validation and error handling for the property value, ensuring that it meets certain criteria or conditions.
• They can perform additional actions or side effects when the property value is changed, such as updating other properties or triggering events.
• They can make the code more readable and consistent, by following the convention of using a method name that starts with set and ends with the property name.

How to Define Public Instance Setters?

We can define public instance setters in JavaScript classes using the set keyword, followed by the method name and a parameter that represents the new value of the property. The method name should match the property name, or be a variation of it. For example, if the property name is name, the setter name can be setName or name. The parameter name can be anything, but it is common to use a name that indicates the new value, such as newValue or value.

The syntax of defining a public instance setter is as follows:

                      
class ClassName {

  // Define the property with an initial value

  propertyName = initialValue;



  // Define the setter with the set keyword

  set setterName(newValue) {

    // Validate and assign the new value to the property

    this.propertyName = newValue;

    // Perform any additional actions or side effects

    // ...

  }

}

                      
                  

Here is an example of defining a public instance setter for a name property in a Person class:

                      
class Person {

  // Define the name property with an initial value

  name = "Anonymous";



  // Define the name setter with the set keyword

  set name(newValue) {

    // Validate the new value, and throw an error if it is not a string

    if (typeof newValue !== "string") {

      throw new TypeError("Name must be a string");

    }

    // Assign the new value to the name property

    this.name = newValue;

    // Log a message to the console

    console.log(`The name of this person is now ${this.name}`);

  }
}
                      
                  

How to Use Public Instance Setters?

We can use public instance setters in JavaScript classes by assigning a new value to the property, using the dot notation or the bracket notation. The setter method will be automatically invoked, and the new value will be passed as the parameter. For example, if we have a person instance of the Person class, we can use the name setter as follows:

                      
// Using the dot notation

person.name = "Alice";



// Using the bracket notation

person["name"] = "Bob";

                      
                  

Both statements will invoke the name setter method, and assign the new value to the name property. They will also log a message to the console, as defined in the setter method.

Conclusion

In this article, we have learned about public instance setters in JavaScript classes. Public instance setters are methods that allow us to set the value of a public instance property of a class. They can provide validation, error handling, and additional actions for the property value. We can define public instance setters using the set keyword, and use them by assigning a new value to the property. Public instance setters can make our code more readable and consistent, and enhance the functionality of our classes.