Device.js
Device.js makes it easy to write conditional CSS and/or JavaScript based on device operating system (iOS, Android, Blackberry, Windows, Firefox OS), orientation (Portrait vs. Landscape), and type (Tablet vs. Mobile).
Stats.js
JavaScript Performance Monitor
Mailcheck
Email domain spelling suggester
Dicebear
DiceBear is an avatar library for designers and developers.
ES5 Shims
ECMAScript 5 compatibility shims for legacy JavaScript engines
Vex
A modern dialog library which is highly configurable and easy to style. #hubspot-open-source
G2 Plot
:dango: An interactive and responsive charting library
Hello.js
A Javascript RESTFUL API library for connecting with OAuth2 services, such as Google+ API, Facebook Graph and Windows Live Connect
LZ String
LZ-based compression algorithm for JavaScript
Framer
Modern Prototyping Tool
Loki JS
javascript embedded / in-memory database
Graphql Editor
GraphQL Visual Node Editor
Lightgallery.js
Full featured javascript lightbox gallery. No dependencies.
Metrics Graphics
A library optimized for concise, principled data graphics and layouts.
Remarkable
Markdown parser, done right. Commonmark support, extensions, syntax plugins, high speed - all in one.
Jquery Transit
Super-smooth CSS3 transformations and transitions for jQuery
Jquery Timeago
Timeago is a jQuery plugin that makes it easy to support automatically updating fuzzy timestamps (e.g. "4 minutes ago").