JavaScript is an extremely flexible language. Although it is mainly associated with scripts that bring websites to life, beneath the surface lies a powerful engine that supports a variety of programming paradigms. If you want to build scalable, clean and easy-to-maintain applications, you need to understand object-oriented programming (OOP) in JavaScript. This approach allows code to be organised into logical „objects” that combine data (properties) and actions (methods), which reflects the way we perceive the real world.
The Basics: ES6 Classes as „Syntactic Sugar”
The introduction of the ES6 standard in 2015 brought with it the keyword class, which has made JavaScript more similar to languages such as Java or C#. It is worth noting, however, that classes in JavaScript are merely a syntactic overlay (so-called. syntactic sugar) to the prototype mechanism that has been in place from the outset.
A class in JavaScript allows you to:
- Constructor: A special method for initialising a newly created object.
- Methods: Functions defined within a class that operate on its data.
- Keyword
this: A reference to a specific instance of an object.
Classes make the code more readable, especially when working in large teams. However, if you want to take code security to the next level, have a look at how the JS superset handles OOP: TypeScript – why is it worth typing JavaScript?.
The four pillars of OOP in JavaScript in practice
To make the most of object-oriented programming (OOP) in JavaScript, one must master the four main principles that govern this paradigm:
- Encapsulation: Hiding internal implementation details and exposing only the necessary interface. In modern JavaScript, we use private fields (beginning with the character
#). - Inheritance: The ability to create new classes based on existing ones (using
extends). ClassCarcan inherit from a classVehicle. - Polymorphism: The ability of different objects to respond differently to the same method call. The same method
.go()will work differently for the objectBicycleiAeroplane. - Abstraction: Modelling only those object attributes that are relevant to the application, whilst hiding the complex logic „under the bonnet”.
The Prototype Chain Mechanism – The Heart of JavaScript
Even if you use classes, the underlying JavaScript uses prototype chain. Every object in JavaScript has a hidden reference to another object, known as its prototype. When you try to access a property that does not exist in a given object, JavaScript looks for it „higher up” in the chain.
Understanding prototypes is key to memory optimisation – methods defined in a prototype are shared by all instances of a given class, rather than being copied into each object individually. This is a fundamental difference compared to the classic inheritance known from C++.
Design Patterns: Proven Solutions in JS
Design patterns are ready-made frameworks for solving the most common programming problems. A knowledge of them is the hallmark of a senior developer.
- Singleton: It ensures that the class has only one instance and provides a global point of access to it (e.g. an application configuration object).
- Factory: It creates objects without the need to specify the exact class of the object being created – ideal when the object type depends on the input data.
- Observer (Pub/Sub): A model in which objects „subscribe” to notifications of changes to another object. This is the basis of reactivity in modern frameworks.
- Module Pattern: It allows you to emulate privacy and organise code into independent units before the introduction of native ES modules.
You can read about how these patterns are evolving towards other paradigms in the article: Functional programming in JavaScript. You can find more advanced examples of pattern implementations on the portal Refactoring Guru.
OOP in modern frameworks
Although React is currently moving towards functions and Hooks, object-oriented programming is still going strong. Angular is almost entirely based on classes and the pattern MVC (Model-View-Controller), where the components are instances of classes managed by Dependency Injection.
An understanding of classes and design patterns makes it easier to switch between technologies – the principles learnt in JavaScript can be applied in PHP, Python or Java. It is always worth checking the detailed definitions and specifications of methods at the source: MDN – Classes in JavaScript.
Write code that will stand the test of time
Object-oriented programming (OOP) in JavaScript It is not just a set of rules; it is a philosophy of writing code that is readable to others and resilient to errors. Mastering classes, prototypes and design patterns is the most important step on the path from being someone who „writes scripts” to becoming a professional software engineer.
At 4ADStudio, we believe in clean architecture. We design systems so that developing them is a pure pleasure, rather than a battle against chaos in the code.
Do you want to improve the structure of your project or implement advanced design patterns in your application? Not sure how to optimise inheritance in your code? Get in touch with us – our experts will help you build a robust and scalable architecture for your digital product!
