React is an open-source JavaScript library for building user interfaces. React is aimed to solve one crucial problem: building large applications with data that changes over time. React is not a full framework like Angular or Ember, it is only the view layer.

Supported by a giant

React is now open source, but it was first developed at Facebook for internal purposes. After a while, Facebook engineers realized that they created something truly awesome and decided to share their project with the world. It is currently, in addition to Facebook, used by Instagram, The New York Times and Khan Academy in production.

Blazing fast

React creates its own virtual DOM where the components actually live. This approach gives an enormous flexibility and an amazing gains in performance because React calculates what changes need to be made in the DOM beforehand and updates the DOM tree accordingly. This way, React avoids costly DOM operations and makes updates in a very efficient manner.

Components based

React gives the ability to create our own components that can be later reused and combined. This is a tremendeous productivity boost and let React scale better with complexity by only dealing with small components with encapsulated behavior.

React can be a game changer for big applications that have performance issues. It can smoothly replace the V of any MVC frameworks and taking care of efficiently rendering the views and let unchanged the rest of the application.