Just getting started on Electron myself. Used by Atom, Slack, Visual Studio... It's worth a look ;)
Electron - Build Cross-Platform Desktop Apps With HTML, JS, CSS
Electron - Build Cross-Platform Desktop Apps With HTML, JS, CSS
To be fair "just" might be over simplifying things a bit. I've been doing this for an application and thinking that it actually would be a benefit to have a different code bases for the desktop and mobile editions. It can be a bit challenging to design for both targets at once.
Also, now that React Native is extending into the Desktop space more directly (with Linux, Mac, and Windows UWP variants), for React you may not need Electron at all.