Classes and Prototypes In Javascript: A Comprehensive Guide 🚀

If you're looking to learn more about object-oriented programming in JavaScript, you've probably come across the terms "classes" and "prototypes". These two concepts are closely related and play a crucial role in understanding how JavaScript works. In this article, we'll explore classes and prototypes in JavaScript, and how they differ from traditional class-based programming languages.

Table of Contents

• What are Classes in JavaScript?
• Defining a Class in JavaScript
• Class Inheritance in JavaScript
• What are Prototypes in JavaScript?
• Creating Objects using Prototypes
• Conclusion
• FAQs

What are Classes in JavaScript?

Classes in JavaScript are a way of defining objects that share similar properties and methods. They are similar to classes in other programming languages like Java or Python, but JavaScript's implementation of classes is based on prototypes. Classes in JavaScript are essentially just syntactical sugar over prototypes, making it easier to write and maintain code.

Defining a Class in JavaScript

Defining a class in JavaScript is quite simple. You use the class keyword followed by the name of the class, and define its properties and methods inside a pair of curly braces. Here's an example of a simple class definition:

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  sayHello() {
    console.log(`Hello, my name is ${this.name}`);
  }
}

In this example, we define a Person class with two properties, name and age, and a sayHello method that logs a greeting to the console.

We also define a constructor function that takes in two arguments, name and age, and initializes the corresponding properties.

Class Inheritance in JavaScript

Class inheritance in JavaScript is achieved using the extends keyword. By using inheritance, you can create new classes that inherit properties and methods from an existing class. Here's an example of a class that inherits from our Person class:

class Employee extends Person {
  constructor(name, age, jobTitle) {
    super(name, age);
    this.jobTitle = jobTitle;
  }

  introduce() {
    console.log(`Hi, my name is ${this.name} and I work as a ${this.jobTitle}`);
  }
}

In this example, we define an Employee class that extends the Person class.

The Employee class has a new property, jobTitle, and a new method, introduce, that logs an introduction to the console.

We also define a constructor function that takes in three arguments, name, age, and jobTitle, and initializes the corresponding properties using the super keyword.

What are Prototypes in JavaScript?

Prototypes are a way of defining objects in JavaScript. Every object in JavaScript has a prototype, which is an object that it inherits properties and methods from.

Prototypes form the basis of JavaScript's inheritance model, which is different from traditional class-based inheritance.

Creating Objects using Prototypes

Creating objects using prototypes is quite simple. You can use the Object.create() method to create a new object that inherits properties and methods from an existing object. Here's an example:

const personPrototype = {
  sayHello() {
    console.log(`Hello, my name is ${this.name}`);
  },
};

const person = Object.create(personPrototype);
person.name = "John";
person.age = 30;

person.sayHello(); // logs "Hello, my name is John"

Conclusion

In this article, we explored classes and prototypes in JavaScript. We learned that classes in JavaScript are just syntactical sugar over prototypes, and that prototypes form the basis of JavaScript's inheritance model. We also learned how to define classes and objects using prototypes, and how to achieve inheritance using classes and prototypes.

JavaScript's implementation of classes and prototypes can be confusing for developers who come from traditional class-based programming languages. However, once you understand the basics, it becomes much easier to write and maintain code in JavaScript.

FAQs

What is the difference between classes and prototypes in JavaScript?

Classes in JavaScript are essentially just syntactical sugar over prototypes, making it easier to write and maintain code. Prototypes form the basis of JavaScript's inheritance model, which is different from traditional class-based inheritance.

How do you define a class in JavaScript?

You use the class keyword followed by the name of the class, and define its properties and methods inside a pair of curly braces.

How do you achieve inheritance in JavaScript?

Inheritance in JavaScript is achieved using the extends keyword for classes, and the proto property for prototypes.

What is the difference between class inheritance and prototype inheritance?

Class inheritance involves creating new classes that inherit properties and methods from an existing class. Prototype inheritance involves creating new objects that inherit properties and methods from an existing object.

Is JavaScript a class-based or prototype-based language?

JavaScript is a prototype-based language, but it also has class syntax as of ES6. However, classes in JavaScript are based on prototypes.