Why React? According the the authors “React is a JavaScript library for creating user interfaces by Facebook and Instagram. Many people choose to think of React as the V in MVC.” They built React to solve one problem: building large applications with data that changes over time. To do this, React uses two main ideas. Simply express how your app should look at any given point in time, and React will automatically manage all UI updates when your underlying data changes. When the data changes, React conceptually hits the “refresh” button, and knows to only update the changed parts.