Minified.js
Replace jQuery or MooTools with a <4kB Library
Responsive Comments
A client-side solution to conditional loading.
Masonry
Layout elements in a grid, like a mason fitting stones in a wall
Gator
Event delegation in Javascript
Tippyjs
Highly customizable vanilla JS tooltip/popover library
Node List.js
NodeList implementation/library - Use the Native DOM APIs as easily as jQuery
Bespoke.js
DIY Presentation Micro-Framework
Motionia
Motionia is a lightweight simplified on demand animation library! https://git.io/motionia
Phantomjs
Scriptable Headless WebKit
Veinjs
Injects CSS into the document (it's a perfectly legal procedure)
Fastdom
Eliminates layout thrashing by batching DOM read/write operations
Handorgel
Accessible W3C conform accordion written in ES6.
Packery
bin-packing layout library
Jquery Waypoints
Waypoints is a small jQuery plugin that makes it easy to execute a function whenever you scroll to an element.
React Virtualized
React components for efficiently rendering large lists and tabular data
Porthole
A proxy to safely communicate to cross-domain iframes in javascript
Mag.js
MagJS - Modular Application Glue