Offline JavaScript REPL for react and ES6+?

While learning react & ES6, I find it surprisingly difficult to evaluate React code (some involving ES6) in an offline REPL type environment (with nodejs).

First of all, ES6 style imports in Node.js REPL is a problem. As the linked question says, I can convert import react to require('react'), but what about.css` files? How do I convert something like these?

import './index.css'

Secondly, how do I evaluate JSX? I am evaluating the following from react quick start

const element = (
  <h1>
    Hello, {formatName(user)}!
  </h1>
);

using atom, with the eval-jaavascript package installed. After hitting cmd-i, I get an error about

SyntaxError: Unexpected token < 
...

How can I fix node or atom configurations to be able to evaluate the above lines?

The example runs OK with npm start, and I know there are on line REPL's. But I just like being able to evaluate code segments in an offline environment in the old fashion line-by-line.

via tinlyx