What is React

React is a UI library developed at Facebook to facilitate the creation of interactive, stateful & reusable UI components. It is used at Facebook.com and Instagram.com is written entirely in React.

But it's important to point out what the React library itself is not...

• React is NOT a UI component library (does not come with any pre-build components)

• React does NOT contain any service injection or other bootstrapping of files

• React does NOT contain any router or DOM handlers

• React does NOT have a template system

With React it's all about rendering state using components. Let's go and see how the components are written.