We already stated that ReactJS is JavaScript library used for building reusable UI components. Definition can be found on React official documentation − React is a library for building composable user interfaces. It encourages the creation of reusable UI components which present data that changes over time. Lots of people use React as the V in MVC. React abstracts away the DOM from you, giving a simpler programming model and better performance. React can also render on the server using Node, and it can power native apps using React Native. React implements one-way reactive data flow which reduces boilerplate and is easier to reason about than traditional data binding. React Features JSX− JSX is JavaScript syntax extension. It isn't necessary to use JSX in React development, but it is recommended. Components− React is all about components. You need to think of everything as a component. This will help you to maintain the code when working on larger scale projects. Unidirectional data flow and Flux− React implements one way data flow which makes it easy to reason about your app. Flux is a pattern that helps keeping your data unidirectional. License− React is licensed under the Facebook Inc. Documentation is licensed under CC BY 4.0. React Advantages React uses virtual DOM which is JavaScript object. This will improve apps performance since JavaScript virtual DOM is faster than the regular DOM. React can be used on client and server side. Component and Data patterns improve readability which helps to maintain larger apps. React can be used with other frameworks. React Limitations React only covers view layer of the app so you still need to choose other technologies to get a complete tooling set for development. React is using inline templating and JSX. This can seem awkward to some developers.