Frameworks like this have come and gone in the last 10 years. I'm not convinced that using this will save you time in the long run. You need to invest a ton of time learning the ins and outs of these frameworks to get stuff done. There are always limitations compared to real native solutions. I think the time is wiser spend understanding the iOS and Android platforms itself.

There is also a big chance that Facebook, Google or whoever will drop their project at some point leaving you hanging and having to rewrite everything again to native or the next multiplatform framework.