Stencil is a compiler that generates Web Components (more specifically, Custom Elements). Stencil combines the best concepts of the most popular frameworks into a simple build-time tool.
Stencil takes features such as
Virtual DOM
Async rendering (inspired by React Fiber)
Reactive data-binding
TypeScript
JSX
and then generates standards-based Web Components with these features baked in.
Prepack is a tool that optimizes JavaScript source code: Computations that can be done at compile-time instead of run-time get eliminated. Prepack replaces the global code of a JavaScript bundle with equivalent code that is a simple sequence of assignments. This gets rid of most intermediate computations and object allocations.
Compass is an open-source CSS Authoring Framework.
Ideone is an online compiler and debugging tool which allows youto compile source code and execute it online in more than 60 programming languages.