Lychee JS
Environment-Independent JavaScript engine (HTML5 Canvas, V8GL, WebGL, native OpenGL, NodeJS)
Angular Validation
Customizing Form Valid Message in AngularJS
Parallax
Parallax Engine that reacts to the orientation of a smart device
LZ String
LZ-based compression algorithm for JavaScript
Vue
Intuitive, fast & composable MVVM for building interactive interfaces.
Char Funk
a Unicode character utility for JavaScript
Pure
PURE Unobtrusive Rendering Engine for HTML
jQuery Migrate
APIs and features removed from jQuery core
Cytoscape.js
A JavaScript graph library for analysis and visualisation (compatible with CommonJS/Node.js, AMD/Require.js, jQuery 1.4+, Bower, npm, and plain JavaScript)
Backgrid
Finally, an easily stylable semantic HTML data grid widget with a Javascript API that doesn't suck.
JS xls
Javascript XLS (Excel 97-2004 spreadsheet) parser and (one day) writer
Nightwatch
UI automated testing framework based on node.js and selenium webdriver
Veinjs
Injects CSS into the document (it's a perfectly legal procedure)
Superagent
Ajax with less suck - (and node.js HTTP client to match)
Args.js
Create javascript functions with optional, default, grouped and named parameters.