Node.js

Highlight.js is a syntax highlighter written in JavaScript. It works in the browser as well as on the server. It works with pretty much any markup, doesn't depend on any framework and has automatic language detection.   Highlight.js - Features: 92 languages and 49 styles (live demo) automatic language detection multi-language code highlighting available for node.js works with any markup compatible with any js framework  

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser and offers an integrated solution to work with numbers, big numbers, complex numbers, units, and matrices. Powerful and easy to use.   Math.js - Features: Supports numbers, big numbers, complex numbers, units, strings, arrays, and matrices. Is compatible with JavaScript's built-in Math library. Contains a flexible expression parser. Supports chained operations. Comes with a large set

WordCount.js is a client-side JS and Node.js library that counts bytes, words, lines, chars, and calculates the longest line of a file using the HTML5 File API.  When a file is uploaded using the file input element with the given input selector then the number of bytes, words, lines, chars, and the longest line in the uploaded file are calculated and then callback is called.  

JointJS is a modern HTML 5 JavaScript library for visualization and interaction with diagrams and graphs. It can be used to create either static diagrams or, and more importantly, fully interactive diagramming tools and application builders. JointJS makes it easy to create visual languages & tools of various kinds.   The event-driven nature together with MVC architecture of JointJS makes it easy to plug-in any backend application.   JointJS - Features: basic diagram elements (rect, circ

LESS is a dynamic stylesheet language, it extends CSS with dynamic behavior such as variables, mixins, operations and functions. LESS runs on both the server-side (with Node.js and Rhino) or client-side (modern browsers only).   As an extension to CSS, LESS is not only backwards compatible with CSS, but the extra features it adds use existing CSS syntax. This makes learning LESS a breeze, and if in doubt, lets you fall back to CSS.  

CamanJS is canvas manipulation in Javascript. It's a combination of a simple-to-use interface with advanced and efficient image/canvas editing techniques.   It is very easy to extend with new filters and plugins, and it comes with a wide array of image editing functionality, which continues to grow. It's completely library independent and works both in NodeJS and the browser.