React.js is a JavaScript library for web developers, used for building application interfaces. It was created for the Facebook newsfeed. It’s the technology that allows Facebook to show different content on a single page without reloading the website. Now a lot of other leading companies use it, with Paypal, Netflix and Apple among them.
The important thing about React is that it’s not the same as JavaScript frameworks, which enable developers to build complete, functional applications. That is not possible with React alone, as all it is, essentially, is a powerful tool to render HTML elements in web and mobile (with React Native) applications.
It forces front-end developers to involve software engineering principles, code compilation and static analysis in their process.
React isn’t a front-end development “silver bullet”, but it perfectly solves the problems it’s been designed to solve. It’s very useful in web applications where content on a page constantly changes.
This technology is fairly easy to learn because of its simplicity, and the fact that it requires only knowledge of HTML and CSS to use it. Applications built with React.js are easy to test, and easy to debug.
Using React.js, developers create fast UI components for apps which generate large amounts of dynamic content in a single view (Instagram is probably the most visual example of such an app).
React saves a lot of time in cross-platform app development, because it is built on a principle of reusing code, which greatly simplifies the process of developing the same app for web and mobile.
It is a well designed technology, founded on the best principles in front-end development, which means that it virtually enforces good design and UI practices. React is probably only going to grow in popularity, because it is a core component for building apps based on components – and componentization is becoming a new standard in web development.
Componentization means incorporating multiple smaller user interfaces for performing different functions, which combined all together make up the whole application.