Because I think that the best css/js framework is composed by many agnostic micro libraries.

JavaScript

Match sorter
Simple, expected, and deterministic best-match sorting of an array in JavaScript
https://github.com/kentcdodds/match-sorter

Vue

Vue gesture https://github.com/vueuse/gesture
Vue Motion https://github.com/vueuse/motion
- useSpring: https://motion.vueuse.org/api/use-spring.html

Sass MQ

A Sass mixin that helps you compose media queries in an elegant way.

My favourite to make perfectly customized media queries

https://github.com/sass-mq/sass-mq

LazySizes

High performance and SEO friendly lazy loader for images (responsive and normal), iframes and more, that detects any visibility changes triggered through user interaction, CSS or JavaScript without configuration.

Amazingly powerfull

https://github.com/aFarkas/lazysizes

Flickity

Touch, responsive, flickable carousels

Not perfect, but better than buggy owl carousel

https://github.com/metafizzy/flickity

Toggles Switches

A declarative pattern for applying CSS states and animations based on user interaction

For things like responsive nav

https://github.com/digitalsurgeons/toggles-switches

Impetus

Agnostic utility for adding momentum to anything. It's like iScroll, except not for scrolling. Supports mouse and touch events.

Simple but very limited (no callbacks)

https://github.com/chrisbateman/impetus

Sass burger

A Sass mixin for creating hamburger icons.
https://github.com/jorenvanhee/sass-burger

Needs jQuery

Zoom.js

Medium's Image Zoom for jQuery
https://github.com/fat/zoom.js

Untested

Flow.js

A JavaScript library providing multiple simultaneous, stable, fault-tolerant and resumable/restartable file uploads via the HTML5 File API.
https://github.com/flowjs/flow.js

Dragdealer

Drag-based JavaScript component, embracing endless UI solutions

Untested but very promising

https://github.com/skidding/dragdealer

maximelebreton/front-end-developer-toolkit.md