ReactJS - Introduction

ReactJS is a free and open-source front-end JavaScript library which is used to develop various interactive user-interfaces. It is a simple, feature rich and component based UI library. When we say component based, we mean that React develops applications by creating various reusable and independent codes. This UI library is, thus, widely used in web development.

ReactJS can be used to develop small applications as well as big, complex applications. ReactJS provides minimal and solid feature set to kick-start a web application. React community compliments React library by providing large set of ready-made components to develop web application in a record time. React community also provides advanced concept like state management, routing, etc., on top of the React library.

React versions

Reactjs library was founded by Jordan Walke, a software engineer at Facebook in 2011. Then the initial version, 0.3.0 of React is released on May, 2013 and the latest version, 17.0.1 is released on October, 2020. The major version introduces breaking changes and the minor version introduces new feature without breaking the existing functionality. Bug fixes are released as and when necessary. React follows the Semantic Versioning (semver) principle.

What is the need for ReactJS?

Even though there are various libraries that provide a medium to develop user-interfaces, ReactJS still stands tall in terms of popularity. Here's why −

  • Component Based − ReactJS makes use of multiple components to build an application. These components are independent and have their own logic which makes them reusable throughout the development process. This will drastically reduce the application's development time.

  • Better and Faster Performance − ReactJS uses Virtual DOM. Virtual DOM compares the previous states of components of an application with the current states and only updates the changes in Real DOM. Whereas, conventional web applications update all components again. This helps ReactJS in creating web applications faster.

  • Extremely Flexible − React allows developers and teams to set their own conventions that they deem are best suited and implement it however they see fit, as there are no strict rules for code conventions in React.

  • Creates dynamic applications easily − Dynamic web applications require less coding while offering more functionality. Thus, ReactJS can create them easily.

  • Develops Mobile Applications as well − Not only web applications, React can also develop mobile applications using React Native. React Native is an open-source UI software framework that is derived from React itself. It uses React Framework to develop applications for Android, macOS, Web, Windows etc.

  • Debugging is Easy − The data flow in React is unidirectional, i.e., while designing an app using React, child components are nested within parent components. As the data flows is in a single direction, it gets easier to debug errors and spot the bugs.


Few popular websites powered by React library are listed below −

  • Facebook, popular social media application − React was originally developed at Facebook (or Meta), so its only natural that they use it to run their application. As for their mobile application, it uses React Native to display Android and iOS components, instead of DOM. Facebook's codebase now includes over 20,000 components and uses the React version that is public.
  • Instagram, popular photo sharing application − Instagram is also completely based on React, as it is powered by Meta as well. The main features to show its usage include Geo-locations, Hashtags, Google Maps APIs etc.
  • Netflix, popular media streaming application − Netflix switched to React in 2015. The factors that mainly influenced this decision are the 1) startup speed to reduce the processing time to render the homepage and enabling dynamic elements in the UI, 2) modularity to allow various features that must coexist with the control experience and 3) runtime performance for efficient UI rendering.
  • Code Academy, popular online training application − Code Academy uses React as the "script is battle-tested, easy to think about, makes SEO easy and is compatible with legacy code and flexible enough for the future".
  • Reddit, popular content sharing application − Reddit is also developed using React from the scratch.

As you see, most popular application in every field is being developed by React Library.

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