React JS is a JavaScript library to build applications, user interfaces, and reusable UI components. React JS was launched in 2013, developed by Facebook and a community of developers. React JS is the most popular front-end framework helps in designing interactive UIs. React JS can be used to develop new features without rewriting the existing code. We can combine other JavaScript frameworks like Angular JS
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You can watch this video on React JS course for beginners to learn more about React JS: