React Native
Doing some playing with react native at the moment and can say it's refreshing (although Swift is nice to use, especially compared to the bloat that is Java for Android)
I used to do native iOS apps in the past, but I've always been more of a web developer than native. This winter, I did a client project in React Native (http://goshakkk.name/works/12min-mobile/) and the experience has been very positive on the iOS side (RN + Android is another story...)
Almost everything you know about React.js holds true in RN. The CSS-like styling and layout with Flexbox are a godsend. ES6 with Flow is type safe, mostly.