Flutter - https://flutter.io/ , but it's in Dart!

I heard about https://weex-project.io/ by way of the Vue docs. There might be other projects too

There is Appcelerator Titanium which has been in the javascript native mobile app game for 5+ years.

https://www.appcelerator.com

I used Appcelerator Titanium to build a couple of apps a few years ago (2011–2012).

The positive: If you know JavaScript, you can get started quickly because they provide a JavaScript API and all your code is in JavaScript. Under the hood the JavaScript connects to native code. So you get a native look and feel on iOS and Android. You have a single codebase.

The negative: Back then it was impossibly hard to get an app working and/or looking correctly on both iOS and Android at the same time because Titanium was full of bugs. So many bugs. This is because for each platform they have to provide native code. Sometimes their iOS code had bugs, sometimes their Android code. It was absolutely frustrating. I often had to find workarounds which caused a lot of delay so I had to double down to keep the deadline. Titanium was a reason I quit that job after 1.5 years.

On paper it’s nice, but the implementation was terrible. I went back to web apps and have since been happy.

It seemed to me Appcelerator sort of abandoned the smaller/hobbyist/indie market for enterprise. I was using it in 2013/2014 and went to one of their conferences in 2014 - activity seemed to really slow to a crawl in public (hyperloop was announced, and the demo looked great, but I never saw much after that).

$40/month, but no visual builder. Eclipse-based IDE tooling (which was always flakey ime). $100/month/seat to get hyperloop and visual builder. Still not sure what 'arrow' is exactly.

The demos always looked good, but my day to day was... frustrating after a while. Possibly could have stuck with it and justified with "sunk cost" but I started looking more closely at cordova stuff. Yes, it's not pure 'native' (why I liked titanium) but the ecosystem is more flexible (or so it seems).

I've been using Titanium for years. Still do. It can be frustrating at times yes, but through using it so long, I've now learned enough Objective-C and Java to fix things or build modules to add functionality. Not enough to build an app, but it's been an enjoyable learning curve.

Turbolinks? https://github.com/turbolinks/turbolinks-ios

Xamarin with Xamarin Forms Xaml

All of those comparisons are missing the point.

RN is not perfect, but it's leagues ahead of Cordova, Xamarin, and etc in a combination of performance and easiness of UI development.

Cordova comes to mind (in the "write 'native' apps like web apps" sense, at least).

Ionic (2) ? I've been using that with great results.

FreePascal compiles to Android and iOS.

Embarcadero Firemonkey.