Ninja UI is described as 'Ninja User Interface, the jQuery plugin for lethal interaction' and is an website in the Development category. There are more than 10 alternatives to Ninja UI, not only websites but also apps for a variety of platforms, including Mac, Windows, Linux and Self-Hosted solutions. The best alternative is React, which is both free and Open Source. Other great sites and apps similar to Ninja UI are UIkit (Free, Open Source), Semantic UI (Free, Open Source), Purecss (Free, Open Source) and jQuery UI (Free, Open Source).
Riot lets you build user interfaces with custom tags using simple and enjoyable syntax. It uses a virtual DOM similar to React but faster. Riot is very tiny compared to industry standards. We think there is a clear need for another UI library.