React JS is JavaScript library used for building reusable UI components. According to React official documentation, following is the definition

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, offering 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 the boilerplate and is easier to reason about than traditional data binding.

React Advantages

• Uses virtual DOM which is a JavaScript object. This will improve apps performance, since JavaScript virtual DOM is faster than the regular DOM.

• Can be used on client and server side as well as with other frameworks.

• Component and data patterns improve readability, which helps to maintain larger apps.

React Limitations

• Covers only the view layer of the app, hence you still need to choose other technologies to get a complete tooling set for development.

• Uses inline templating and JSX, which might seem awkward to some developers.