What is React.js used for? What’s worth knowing?

Marlena Walburg

When planning to build a web or mobile application, it is impossible not to come across React.js. This is no surprise because it is an extremely popular JavaScript technology, which has been on the top for a good few years. Moreover, React.js carries a lot of opportunities, so raptures over it are not just idle talk. Facebook, Instagram, Pinterest and even Netflix use it. The entry threshold of React.js is relatively easy, so less experienced programmers can use it, and additionally, it is constantly developed, thanks to which it has a large community. Besides, it is very well received by Google robots in terms of SEO, as websites created with its use are very fast and relatively light. So it is not difficult to conclude that both business and technological benefits are a feature of this JavaScript library. What is worth knowing about it, what digital products it will be suitable for, and whether there is something to admire – this is what we are asking today.

What is React.js?

React.js is a popular and willingly used JavaScript library that is used to create graphical interfaces of web applications. It was developed by Jordan Walke, a Facebook developer, and inspired by an HTML component library for PHP – XHP. Often used to create Single Page Applications, but it can also be the basis of mobile applications. React.js was created for the needs of Facebook. Company’s engineers were looking for a way to build dynamic yet highly efficient interfaces, resulting in this universal library. Originally React.js only intended for internal projects, but in 2013 it was made available by Facebook on an open-source basis. Now, React.js is the most popular front-end JavaScript library for web development.

What are the React.js features?

Before we move on to the pros and cons of React.js, let’s focus on notable features of the technology.


The components are autonomous, reusable bits of code. They are used for the same use as JavaScript functions, but run in isolation and return HTML. React allows you to define components as classes or functions through properly implemented methods and inheritance. Each component has several lifecycle methods that you can override so that your code runs at a specific time in your program.

We can list several types of components, including two main ones, functional and class. A functional component is a function that takes props and returns the JSX code to render to the DOM tree. They do not have state or lifecycle methods. Class components are used with ES6 class syntax. They are more complex than functional components, including constructors, life-cycle methods, state management, etc. Class components can accept props if needed. In React, props and state are two types of “model” data, plain JavaScript objects.

Virtual DOM

A notable feature of React.js is the virtual Document Object Model, or shortly called the DOM. React.js creates a cache of the data structure in memory, computes the resulting differences, and then efficiently updates the browser DOM displayed, which we call the reconciliation process. This allows the developer to write code as if the entire page is rendered with each change, while the React libraries only render the subcomponents that change. This process of selective rendering provides a significant performance boost and also saves the effort of recalculating CSS style, page layout, and full-page rendering. 


JSX (or JavaScript XML) is an extension of JavaScript syntax. Looking similar to HTML, JSX provides a way to structure the rendering of components using a syntax familiar to many developers. React components are typically written using JSX, although they can also be written in plain JavaScript. JSX is similar to the syntax of another Facebook extension for PHP – XHP.

One-way data binding

ReactJS is designed to follow one-way data flows or one-way data binding. The one-way data binding process gives you greater control over the entire application. Since the components are to be immutable and the data they contain cannot be changed, if the data flow is in a different direction, it requires additional functionality. 

To support this concept, the architecture called Flux was introduced to React.js. Flux is a pattern that helps keep your data unidirectional. This makes the application more flexible leading to increased performance.

Pros of React.js

We already know that React.js is a hugely liked technology, so check what makes it happen:

  • Easy to learn – learning ReactJS, as opposed to other technologies of such kind, is thought to be a more manageable and enjoyable process. By understanding ReactJS, you can start building highly responsive applications right away. It allows you to easily view and study the functions of developing mobile and web applications without requiring any patterns, templates or architecture. It has built-in formulas and functions that can be combined to produce effective designs in less time than it would take to create code line by line. Knowing JavaScript syntax can be useful, and most often, JS developers research ReactJS, but it is not a must.
  • Faster rendering and reliable performance – the launch of Virtual DOM by Facebook developers has made React JS one of the more effective and less impeded technological solutions for application development. The DOM (Document Object Model) has a large influence on the potential load on the application due to its structure. DOM methods allow programmatic access to the tree, and with them, you can change the structure, style or content of a document. Since the DOM of modern websites is huge, updates can take a long time, slowing the overall performance of the web application. The browser regularly checks for any changes to the DOM and updates it accordingly. The change may be caused by user input, inquiry, data receipt etc. The browser updates the DOM every time a change occurs. The use of a Virtual DOM, which is smaller and can be updated quickly, has a very positive effect on application performance. Only after interaction between the website and the virtual DOM is the actual DOM updated. The result is providing a better user experience, higher performance, and great facility.
  • Facilitates writing components – amid all the useful functions of ReactJS are also those that visualize what is occurring in the JavaScript code that operates on graphical interfaces. It is a JSX. This is an optional JavaScript syntax extension with the ability to insert tags, which makes it much easier to write your components. It also helps React display a more useful error and warning information, accepts HTML quoting, and makes it easy to render subcomponents. In practice, it’s a set of shortcuts for writing “React elements” with a few rules to keep your code transparent and milder.
  • Code reusability – ReactJS supports building reusable components. Once created, such a UI element can be used in other parts of your code, in various other projects, sometimes with little or no modification. It is also combined with the possibility of using free libraries of ready-made components. It also positively influences the key business features, i.e. saving time and money thanks to the lack of the need to write everything from the very beginning.
  • SEO friendly – due to the current trends, this feature is extremely useful. JavaScript frameworks are ordinarily not very SEO favourable, and web applications lose the position in search engines with optimized pages. The ability to respond to common problems with search engines is another advantage of using the React JS framework. It enables developers to create engaging user interfaces that can be easily browsed through various search engines.
  • Downward data flow = more stable code – many ways to limit errors in your code are available, and framework and library developers are aware of it. When it comes to ReactJS, one of the processes that help with this is a one-way flow of data, also known as downward data flow. This means that data is transferred between items in ReactJS only one way. As a result, developers gain additional support in debugging and bug prevention.
  • Extensively used and popular – ReactJS is a popular choice also among well-known global brands. Successfully implemented applications, or websites of companies such as Airbnb, Tesla, Netflix and others prove that you can achieve a lot with this technology.

Cons of React.js

Is it a perfect technology, without flaws? We wish so, but unfortunately no. There are some downsides to React.js:

  • The high pace of development – it is both a disadvantage and an advantage depending on the project. However, because the library is constantly and rapidly changing, some developers may feel uncomfortable re-learning new ways to implement certain elements. It can be difficult for them to work with the ever-changing technology. After all, it requires them to always be up to date on their abilities and learn new ways of doing things.
  • Poor documentation – a common problem when technology is constantly updated. React.js modernises and speeds up so quickly that there is no time to do documentation. To remedy this, developers write tutorials and instructions on their own as new versions develop.
  • Not a full-stack tool – ReactJS only covers application UI layers, so technology is still needed to get a complete set of project development tools.
  • Third-party libraries – when developing projects with React.js, you almost always need to use additional libraries. If someone likes to have all their tools at hand at once without having to look further, they may feel disappointed. The advantage of this situation is the lightness of the React library, which is designed for a small number of tasks but does them well.
  • Problematic JSX – ReactJS uses JSX to mix HTML and JavaScript, which can have many advantages, but some developers find JSX a barrier, especially for new developers. They mainly complain about its complexity in the learning curve.

What is React.js used for?

React.js is a very universal technology that is used to build interfaces, and therefore everything that allows users to interact with devices. Interfaces can be found everywhere, from mobile applications to websites, hence there are many use cases for this library.

Single Page Application

The flagship example of using Reactjs is a Single Page Application. React SPA works inside the browser and does not require the user to reload the page. Also, when a user navigates through a SPA, they will continue to interact with the same page without interacting with a completely new page. Many well-known applications that are used every day are SPAs, such as Gmail, Google Maps or Facebook.

Social platforms

Social applications are one of the common React.js use cases. Creating a social network is recommended almost always as a single page application, as HTML templates do not work well with dynamic page updates. This is how Facebook started as a regular website and gradually moved to a single page app. With rapid development, great user experience, and high responsiveness capabilities, React.js is a great choice for social networking.

E-commerce platform

The eCommerce sites are usually very complex, consisting of many different elements, filters, APIs, etc. These parts should be highly independent of each other. Reactjs helps developers implement all of these features by creating separate components. Additionally, they are easy to scale. The ability to reuse components, which is a feature of React, can positively affect the development time of such a platform.

Enterprise applications

Since the entire application can be neatly broken down into smaller reusable UI elements, many developers find React.js the most suitable for enterprise application development. React.js’ component-based architecture helps tackle legacy stack problems with very fast adaptation and implementation cycles. Of course, the speed of development, the stability of React.js supported and improved by Facebook, and the popularity of this technology among developers are also the reasons why companies decide to use React.js. 

Cross-platform mobile apps

With the React Native framework, and therefore also using React.js, cross-platform mobile applications can be created. If Reactjs is already in use in a web app, it’s much easier to upgrade from the mobile version as well as migrate the web version entirely to React Native. The React Native mobile app works like a native app on IOS and Android. By employing Reactjs developers, you will also be able to create React Native mobile applications.

React.js App Examples

According to StackShare, 9243 companies use React in their technology stacks (in January 2020). They include very well-known global brands, so it is respected technology among market leaders, too. Below are some examples of a successful React.js implementation.


In the beginning, Airbnb was just a website with growing traffic on mobile platforms. After a while, the developers realized that to meet the needs of their mobile users, they have to invest additional resources in mobile platforms. Several years later, after transformation, the team decided on a solution whose core is ReactJS – the React Native cross-platform framework. This ended in fast development, as well as increased traffic and gaining new users.


Among the applications using ReactJS, its inventors’ products could not be lacking. Facebook is the most popular social network nowadays, and its mobile app is one of the commonly used apps in the world. To improve the mobile experience and meet Facebook’s high demands, they first created an open-source library, which is discussed by us, React JS, and then their cross-platform framework, React Native. Currently, it is one of the most widely used frameworks for developing Android and iOS applications.


An interesting example of React, js implementation is Graphiq. It is a platform that connects professionals wanting to hire designers with the right creative talent, helping to succeed in projects on time, on budget and deliver the highest quality product. We developed it from scratch in BinarApps, the platform combines several technologies, including React.js. It is currently a leader in the creative sector and provides customers with the highest value.


Choosing the right technology for developing digital products is not an easy thing. Hence, it is good to be familiar with them and know their advantages, disadvantages, and purpose, just like in the case of React.js. Undoubtedly, this library is worth the attention paid to it by the IT community. When considering the use of React.js, take into account that it is subject to further development and is strongly supported by Facebook. The community is continually working on developing options and adapting features to meet emerging needs. It can, therefore, be safely assumed that this is a library that will not stand still and, thanks to the efforts put in, will be constantly updated. It is also a premise that the future of React.js should be stable and that React.js itself will be a safe choice. 

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Marlena Walburg

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