JavaScript has a function called “class” which can be used for creating user-defined types and new data types. However, it does not have the same capabilities as C++ or Java classes. JavaScript’s class is more similar to what other languages call “traits.” Therefore, while JavaScript does have a class keyword, it works differently than classes in other languages.
In addition, because JavaScript is a prototype-based language, objects can inherit properties and methods from other objects. This makes it possible to create “class-like” structures in JavaScript without using the class keyword. Overall, while JavaScript does have some features that are similar to classes in other languages, it is not a true class-based language.
So, does JavaScript have classes? Let’s address this question in more detail in this post.
Does JavaScript Have Classes?
Yes, JavaScript has a class keyword. However, JavaScript’s class keyword works differently than the class keywords in other languages.
In other languages, the class keyword is used to create a new class. This class can then be used to create objects. The class defines the properties and methods that will be available to objects created from the class.
In JavaScript, the class keyword is used to create user-defined types. User-defined types are like custom data types. They can be used to create objects, but they do not have the same capabilities as classes in other languages.
JavaScript’s class keyword is more similar to what other languages call “traits.” Traits are a way of sharing behavior between classes. They are not full-fledged classes, but they do allow you to reuse code.
Object Oriented Programming In JavaScript Before ES6
Prior to ES6, JavaScript was still an object-oriented programming language. But, instead of classes, JavaScript had constructor functions and the prototype-based inheritance.
A constructor function is just a regular function that is used with the new keyword to create an instance of an object. For example, we can have a constructor function for creating cars like this:
function Car(model, year, miles) {
this.model = model;
this.year = year;
this.miles = miles;
}
The above constructor function will create an object with three properties: model, year, and miles. And, we can create new instances of the Car like this:
var civic = new Car("Honda Civic", 2009, 20000);
console.log(civic);
// output: { model: "Honda Civic", year: 2009, miles: 20000 }
As you can see from the above example, using a constructor function is just like using a class in other programming languages. But there is one key difference between classes and constructor functions which is that in JavaScript, a constructor function does not have methods but instance objects created from constructor functions can have methods.
Methods can be added to the instance objects created from the constructor function by using the prototype property as follows:
Car.prototype.toString = function () {
return this.model + " has done " + this.miles + " miles";
};
Now, if we create a new instance of the Car and call its toString method, it will give us the following output:
var civic = new Car("Honda Civic", 2009, 20000);
console.log(civic.toString());
//output: "Honda Civic has done 20000 miles"
As you can see, methods are added to the prototype property of the constructor function so that all the instances created from the constructor function can inherit those methods.
In JavaScript, all the objects created from the same constructor function share the same prototype object. So, when a method is added to the prototype object of a constructor function, it is available to all the objects created from that constructor function.
Introduction Of Classes In ES6
With the release of ES6, JavaScript got support for classes. The class keyword in JavaScript is just syntactic sugar over the existing prototype-based inheritance and does not introduce any new concept that was not already available in JavaScript.
ES6 classes are just like the constructor function discussed above with a few syntactic differences. For example, we can create a Car class in JavaScript using ES6 like this:
class Car {
constructor(model, year, miles) {
this.model = model;
this.year = year;
this.miles = miles;
}
toString() {
return `${this.model} has done ${this.miles} miles`;
}
}
As you can see from the above code, the Car class is just a constructor function with some syntactic sugar. For example, we don’t need to use the function keyword to declare the Car class. In addition, methods are declared inside the body of the class using the same syntax as other programming languages like Java or C#.
With ES6 classes, when we create an instance of a class using the new keyword, there is no need to explicitly call the constructor function as it is done automatically. So, we can simply write:
var civic = new Car("Honda Civic", 2009, 20000);
console.log(civic); // output: { model: "Honda Civic", year: 2009, miles: 20000 }
As you can see, the above code is much cleaner and simpler as compared to the previous code using constructor functions.
ES6 classes also support inheritance using the extends keyword. For example, we can create a subclass of the Car class like this:
class Vehicle {
constructor(model, year) {
this.model = model;
this.year = year;
}
}
class Car extends Vehicle {
constructor(model, year, miles) {
super(model, year); // call parent class constructor function
this.miles = miles;
}
toString() { // overriding parent class method
return `${this.model} has done ${this.miles} miles`;
}
}
As you can see, the Car class inherits from the Vehicle class using the extends keyword. In addition, the super keyword is used to call the constructor function of the parent class.
Finally, the toString() method is overridden in the Car class to provide its own implementation.
So far, we have seen that ES6 classes are just syntactic sugar over existing Prototype-based inheritance and don’t introduce any new concept that was not already available in JavaScript.
Even though classes make working with inheritance much simpler and cleaner, they are not really necessary as everything that can be done using classes can also be done using constructor functions and prototype objects.
Classes just make things more confusing in JavaScript, as people coming from other programming languages might expect things to work in a certain way that is not really the case in JavaScript.
Difference Between A Prototype And A Class
It is important to understand the difference between a prototype and a class, as many people use the terms interchangeably, which can lead to confusion.
A class is just a template or blueprint from which objects can be created. So, a class doesn’t really exist in JavaScript, but rather it is just used as a way of defining how an object should look like.
On the other hand, a prototype is an actual object that exists in memory and that can be used to create new objects. All the objects created from a constructor function share the same prototype object.
In other words, a class is like a recipe for making objects, while prototypes are actual objects that can be used as templates for creating new objects.
Classes are typically used in object-oriented programming languages like Java or C++, while prototypes are used in JavaScript.
Prototype-based inheritance is more flexible than class-based inheritance because it allows us to change the structure and behavior of an object at runtime.
For example, we can add new methods or properties to an existing object without having to change the original definition of the object.
In addition, prototype-based inheritance is more efficient because objects can inherit from other objects, instead of having to inherit from a class.
What Was The Reason Behind Adding Class Keyword In JavaScript?
The class keyword was added in JavaScript to provide a more familiar and intuitive syntax for defining constructor functions and class methods.
Prior to the introduction of the class keyword, the prototype-based inheritance model was used exclusively. While this model is still supported, the class syntax offers a number of advantages.
For one, it makes it easier to declare methods and properties without having to use the function keyword. In addition, classes can be declared in a top-level scope, which is not possible with the prototype-based model. It was also thought that it would make things easier to understand for people coming from other object-oriented programming languages that have the concept of classes.
Finally, the class keyword provides a convenient way to extend existing classes by using the extends keyword. As a result, the class keyword provides a more familiar and powerful way to work with objects in JavaScript.
JavaScript Is Still Prototype-Based And Not Class Based
Even though the class keyword was introduced in JavaScript, the language is still prototype-based and not class-based.
This means that inheritance works differently than in other object-oriented programming languages and that the class keyword does not really introduce any new concept that was not already available in JavaScript.
As we have seen, classes are just syntactic sugar over existing Prototype-Based Inheritance and don’t really add anything new to the language.
If you come from a Java or C++ background, you might expect things to work in a certain way that is not really the case in JavaScript.
What Is The Difference Between Class And Function In JavaScript?
In JavaScript, a class is a blueprint for creating objects. It can be used to define properties and methods that belong to an object, as well as the relationships between different objects.
A function, on the other hand, is a block of code that performs a specific task. It can be assigned to a variable, or invoked directly. In general, classes are used to model real-world objects, while functions are used to perform actions.
However, there is some overlap between these two concepts, and it is possible to create classes that have functions as members. Ultimately, the decision of whether to use a class or a function will depend on the specific needs of your project.
Should I Use Class In JavaScript?
Class is a feature that was introduced in ES6 and is syntax sugar on top of well-known JavaScript patterns. Some developers argue that it adds unnecessary complexity to the language, while others find it essential. So, should you use class in JavaScript?
Advantages
There are a few key benefits to using class. First, it can help to make your code more readable and easy to follow. Class also provides a standard way of creating objects, which can be helpful if you need to work with other developers who may be familiar with different conventions.
In addition, class gives you more control over the behavior of your objects, and it can make it easier to debug and test your code.
Disadvantages
However, there are also some drawbacks to using a class. Some experienced developers argue that class syntax is more complicated than the existing prototype-based inheritance model and that it does not offer enough benefits to justify its use.
And, even though classes were supposed to be used the same way as some other programming languages, there are still some differences that can trip up developers coming from other languages –
Binding Issues
The this keyword is crucial in the class constructor functions, since they deal closely with it. It may cause binding issues, especially if you attempt to pass your class method as a callback to an external routine.
Performance Issues
Creating classes in JavaScript comes with a performance cost, because of the way they are implemented.
Private Variables Are Absent
There is no built-in way to create private variables in JavaScript classes. However, there are a few workaround solutions, such as using symbols or WeakMaps.
Stricter Hierarchies
Classes sacrifice maintainability in favor of flexibility, which isn’t something you want in most JS apps.
Ultimately, whether or not you use classes will depend on your personal preferences and the needs of your project. If you are working on a small project with a limited team, then using class might not be necessary.
However, if you are working on a larger project or collaborating with other developers, then using class could help to make your code more readable and easier to manage.
Alternatives To Class
If you’re not sure whether or not to use class in your project, there are a few alternatives that you can consider. One option is to use the older prototype-based inheritance model.
This has been around for longer and is more widely used, so you may find it easier to work with. Another possibility is to use a JavaScript library or framework that provides its own object-oriented programming model.
For example, React has its own way of creating and working with components, which is similar to classes in other programming languages. Ultimately, the decision of whether or not to use class will come down to your specific needs and preferences.
If you’re just getting started with JavaScript, you may want to stick to the prototype-based inheritance model. However, if you’re looking for more control over your objects, then class may be the right choice for you.
Conclusion – Does JavaScript Have Classes?
No, classes don’t exist in JavaScript in the manner that you might think. However, it does provide a way to create objects and define their properties and methods using the class keyword.
Whether or not you should utilize class in your project is a question of personal taste and requirements. If you’re just getting started with JavaScript, prototypal inheritance may be the way to go. If you want more control over your objects, however, class might be the way to go.
In the end, it will be your specific requirements and preferences that will drive whether or not to utilize classes.