Enable tab completion for JSX with Emmet in Atom

This guide assumes you have the emmet and language-babel packages already installed in Atom

1. Open the keymap.cson file by clicking on Atom -> Keymap… in the menu bar
2. Add these lines of code to your keymap:

'atom-text-editor[data-grammar~="jsx"]:not([mini])':
  'tab': 'emmet:expand-abbreviation-with-tab'

Now open a file with JSX code, type div.myclass, press tab and it should autocomplete to <div className="myclass"></div>! (if it's not properly syntax highlighted, select Babel ES6 JavaScript or JSX as the syntax, this won't work otherwise)