What is React.js Framework?

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Piotr Balbier

Updated Feb 8, 2024 • 13 min read
Defining React.js Framework

React.js is JavaScript framework that is fast, secure, and scalable. It provides a fantastic user and developer experience.

What's more, its popularity is growing as it's supported by Facebook and a vibrant community. React.js is a dominating frontend JavaScript technology, and it's getting more and more popular. According to GitHub, over the last few years, the number of React.js package downloads with NPM vs. the other two popular frameworks - Angular/Core and Vue - has accelerated significantly. Technology use spreads with power laws and it looks like React.js is taking over its category.

If you are wondering which technology to choose for your project, React.js is probably the best choice. Here's a short guide that will explain why.

What does precisely React.js framework do?

React.js framework it's a tool to build UIs - a JavaScript library for building user interfaces. Some software engineers prefer not to call it a "framework" since it gives the developers much more freedom than Angular or Vue.

Just like Angular is supported by Google, React.js is maintained by Facebook and a community of developers. Both are open source and free to use under the MIT license. React.js is only six years old, which makes it a relatively new technology. However, it matured very quickly.

With JavaScript, you can build dynamic applications where the browser performs a substantial part of functions, so they can work without contacting the server. It also allows the data and interface to be updated independently in just a part of an app (without reloading it).

react.js number of downloads per year chart

Source: GitHub: Stack Overflow Trends

React is a tool to build both UI components and whole UIs – everything that concerns putting together visual elements, binding data to those elements, and specifying the logic governing it.

React.js can be used to create user interfaces in JavaScript for different platforms. You can use ReactDOM for web applications, React Native for mobile app development (sharing the majority of code between Android and iOS), and cross-platform hybrid desktop applications with Electron. Recently, Microsoft has also released React Native for Windows.

React.js is a frontend technology, but it can also be executed on the backend (server-rendered) and used for desktop apps.

There are two possible approaches to using modern JavaScript frameworks – client-side rendering, where the browser downloads the code and renders the UI, or server-side rendering, where the UI is rendered on the backend.

The difference between JavaScript solutions (such as React.js) and older technologies is that JS takes over much more of the logic and document manipulation, just as if it was not server-rendered at all.

The main feature of React.js that distinguishes it from other popular JavaScript frameworks is flexibility. You can grab a library and use it to display a simple page or a view, but you can also combine React.js with other tools and use it as a framework that will lay the foundation for a complex application.

The difference between React.js and React Native

React Native has recently become an even more popular buzzword in business circles. That is because Facebook actively promotes it as the best tool for cross-platform mobile app development. React Native uses UI elements written in React.js that can generate native iOS and Android interface components, such as buttons and animations. With React Native you can build applications that work smoothly on iPhone and Samsung or Huawei smartphones sharing the vast majority of the code between the two platforms.

Three key terms you need to know about React.js

There are not many of them, but understanding these basic expressions will help you get a grasp of what it's about.


These are the building blocks that can be put together to create an application. With React.js it's relatively easy to build custom components, which is a very important feature since building custom components is needed in 99% cases and off-the-shelf components usually make up 10-20% of components in a React.js application. You may also go for an existing full-fledged UI library (like Material UI) and simply connect the components with data and custom logic.


It is an extension of JavaScript allowing developers to write views using syntax resembling HTML and XML which t can be mixed with JS to control the logic.


It is a state management library with a vibrant ecosystem, often paired with React.js.

What apps can you build in React.js?

For a start, think about Facebook.

It's made with React.js. In 2012, Facebook Ads became challenging to manage as the social network's web application was larger and included more components.

Mark Zuckerberg stated that relying on HTML5 was one of the biggest mistakes of their organization, promising at the same time to the users (and investors) that Facebook will deliver great mobile experiences soon.

At the same time, the corporation acquired Instagram. In May 2013, React.js was officially launched.

Since then React.js is taking over. New products are being made using it and some of the biggest and most successful digital products are incorporating React.js into their stack. This includes the world’s most renowned applications, such as:

  • Social networks (Facebook, Instagram, Pinterest, Twitter)
  • Sharing economy platforms (Airbnb, Lyft, Uber)
  • Media sites (Yahoo!)
  • Video platforms (Netflix)
  • SaaS tools (SendGrid, Asana, InVisionApp, Zapier)

You can find the complete list of popular digital products using React.js here.

The Netguru team have also built plenty of great products using React.js - Newst, Moonfare and many more, including solutions for Solaris Bank, a Berlin-based fintech.

Facebook created React for their own purposes; most of their web and mobile apps are written using React. At the moment, the social network is in the process of rebuilding the whole platform with React, GraphQL, and Relay.

The most important features of React.js

Here are the five most impressive React.js features chosen by the Netguru team.


In a nutshell, the concept is to "say what, not how". You build the app's user interface creating view after view. With React.js the code focuses on what is displayed rather than what steps should be taken to display it. For a non-coder, the second approach seems more intuitive. And it is indeed quicker to build and debug a screen or component with this method. Declarativeness means great DX (developer experience), which usually translates to great UX.

Component-based approach

You construct apps with React.js using building blocks - components that can be responsible for a UI function (e.g., a button), network communication (e.g., a data fetcher), or much more complex functions, such as managing the state (e.g., Redux Provider). This modular approach makes it easy to implement a design system and show it off (e.g., with Storybook). Components in React.js make for a compelling DX.


React.js is small and quick to download. It doesn't require much work to configure the programming environment. What's more, you don't always have to load the entire application thanks to the code-splitting feature, which can significantly reduce load times of your website or web application. Smooth and fast loading times are crucial for the UX of your product as well as marketing (SEO) because Google promotes sites with short loading times.

Huge ecosystem and flexibility

When choosing a technology for your digital product, you want to use a programming language or a framework that's already popular, and most importantly, that will remain popular in the future. Extensive usage provides you with the most crucial resources - a pool of talented developers knowing the technology and willing to learn and excel in it as well as expanding libraries of components and new areas of application. React.js has it all.

Backward compatibility

It is always great for the software to be able to work with older versions of the libraries it uses (or depends on). However, not many languages and frameworks can provide backward compatibility, because it's expensive. Fortunately, Facebook had to invest in maintaining backward compatibility for its internal corporate use. Some FB apps still run pieces of code created when React was still in its infancy with no compatibility issues.

Talented developers want to use React.js

There must be a reason for React.js to be so popular among developers. It's the most loved and the most wanted web framework according to the Stack Overflow Developer Survey 2019, with 74.5% of developers working with React.js declaring they would like to continue doing so and 21.5% software engineers who don't know React.js stating that they would like to learn it.


All the superpowers mentioned above translate to significant business advantages of the React.js framework. Facebook backs the technology, it's increasingly popular, and young talented developers from all over the world are willing to learn it.

The large talent pool and bright perspectives are fundamental characteristics from the business point of view. Many successful digital projects were forced to rewrite their code into newer technologies, including Facebook.

React.js allows fast & scalable software development

You can build web applications and hybrid mobile apps, fast, with React.js. It's perfect for the modern agile, iterative software design and development approach. With React.js, you can launch an MVP very quickly without sacrificing any of the look and feel nor UX.

Thanks to its modularity, React.js scales up easily. You can bootstrap a product with minimal resources, as well as develop a sizeable single-page application, such as Facebook.

Thanks to the availability and diversity of tooling and companion libraries that are appropriate for different use cases, it's possible to use React to build software from small, lightweight websites, through medium-size portals and apps, to large enterprise-scale systems.

You use apply React.js in any frontend web or mobile application. Here are some scenarios it suits perfectly.

  • If you are facing a medium-to-high complexity application requiring complicated flows on the client side.
  • If you are planning to uild an app requiring a reactive and performant UI.
  • When developing a static website with more or less dynamic content (such as a blog or a landing page). Gatsby.js, a site generator for React.js, is the industry standard for these use cases.
  • When having a performant website or web application is crucial to your business plan.
  • If finding high-quality engineering talent quickly is essential for the success of your project.

All these situations create a perfect storm for React.js usage.

Actually, it's more challenging to name scenarios where React.js is not the right choice. For example, if you are planning to build a simple create, read, update, and delete (CRUD) application, React.js may be overkill.

The same may be true in the case of a simple one-off webpage. However, if your CRUD functions are just a first step for future development, you may consider this technology.

Growing interest in React.js framework

The more companies and individuals use React.js framework because it is getting the ever more flexible, scalable, and safe it gets, since all the community works together to improve the technology. It also gets more accessible, more universal, and simpler to use.

React.js a flexible tool that has many use cases already. It can be implemented in almost any project that requires a frontend with at least some level of complexity. The JavaScript library can be used in startups to quickly release an MVP and grow the product later. React.js proves to be useful for enterprises, where it is used to implement new features quickly.

However, since so many organizations are embracing React.js and so many talented engineers are using and learning to use React.js, it's more likely that, at least in the next few years, we will be surprised by a new reusable component that makes creating React apps even easier than by the technology going out of use.

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