Lots of people use React as the V in MVC. Since React makes no assumptions about the rest of your technology stack, it's easy to try it out on a small feature in an existing project.
It is the fastest way to build web applications in Java. It automates the communication between your server and the browser and gives you a high-level component API for all Vaadin components
Xamarin’s Mono-based products enable .NET developers to use their existing code, libraries and tools (including Visual Studio*), as well as skills in .NET and the C# programming language, to create mobile applications for the industry’s most widely-used mobile devices, including Android-based smartphones and tablets, iPhone, iPad and iPod Touch.
Flutter is a mobile app SDK to help developers and designers build modern mobile apps for iOS and Android.