React

React is a javascript library used for building user interfaces (UI). React is useful and unique from other javascript libraries for a couple main reasons:

1. React is declarative. React makes it simple to create interactive UIs. Developers can create simple views for each state in your application, and React will efficiently update and render just the right components when your data changes. Declarative views make your code more predictable and easier to debug.

2. React is component-based. With React we can create encapsulated components that we are able to piece together to make complex user interfaces. Since component logic is written in JavaScript instead of templates, you can easily pass rich data through your app and keep state out of the DOM.

Further reading: https://reactjs.org/