A free and modern UI toolkit for web makers based on the popular Bootstrap 4 framework.

flatpickr is a lightweight and powerful datetime picker.
Lean, UX-driven, and extensible, yet it doesn’t depend on any libraries. There’s minimal UI but many themes. Rich, exposed APIs and event system make it suitable for any environment.
This “lean” philosophy translates to less size and better performance, with a bonus of not having to load 8 libraries for a calendar.

Select2 is a jQuery based replacement for select boxes. It supports searching, remote data sets, and infinite scrolling of results.