JSX is a syntax extension for JavaScript. It was written to be used with React. JSX code looks a lot like HTML.

What does “syntax extension” mean?

In this case, it means that JSX is not valid JavaScript. Web browsers can’t read it!

If a JavaScript file contains JSX code, then that file will have to be compiled. That means that before the file reaches a web browser, a JSX compiler will translate any JSX into regular JavaScript.

Codecademy’s servers already have a JSX compiler installed, so you don’t have to worry about that for now. Eventually we’ll walk through how to set up a JSX compiler on your personal computer.