Learn the key concepts behind React and how to use JSX elements and components to build lean and fast web front ends React, also known as ReactJS, is an open source JavaScript library for building ...

Now, here’s where the special nature of React comes in. Besides normal HTML, CSS, and JavaScript, the bulk of your React code will be written in JSX.

Beyond the usual quick tips, let's look at both the business case and the technical side of keeping React bundles lean.