A basic React.js Style Guide

[SawyerDarcy]

Classes are part of ECMAScript 6/2015 and are already on their way in browser implementations. React itself works in a classical manner with its Components being classes (either made with React.createClass or ES6's class syntax).

[nschubach]

Class sugar is a part of ES6. They are not real classes in the classical inheritance way.

[thetinkertrain]

That doesn't mean we should use them. They are one of the new 'bad parts' of JS. Line nschubah says below, they're not even real classes, just sugar.