I've embraced TypeScript to the max and with the project's monthly release schedule, I've been involved in learning the new additions to the language. That includes using React.js and Redux with TypeScript, which turns out to be a great combination.
For a side project that I'm working on, I decided to use React Native, so I had to learn a bit about RNative's ecosystem and differences to React.
With the introduction of Kotlin as an officially supported language for Android Development, I've decided to invest some time learning it. It's too early to say my overal impressions yet, but for now I feel it's worth learning.
Rust won my attension a couple of months ago and I've been messing with it for some time. It's gaining traction really fast and its performance is incredible. So, I will definitely invest some time in it.