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Web developers are pretty lazy theese days to draw design from scratch in Photoshop and produce markup and CSS. It's much easier to use one of those prototyp apps with popular UI frameworks like Twitter Bootstrap or Foundation. Divshot, Easel, JetStrap are good to start with.

Node.js based static site generators allow you to build fast, secure and light websites, including blogs. Examples: wintersmith, poet, enfield.

JavaScript mapping libraries provide a way to display geodata. Sometimes they aggregate various mapping services behind a single interface.

As WebGL can be difficult to work with as is there are various JavaScript libraries that hide the tricky bits and provide a nicer API to work with. Examples: three.js, PhiloGL, csg.js.

JavaScript selector libraries, such as Sizzle, make it easier to access the content of DOM structure and provide more versatile syntax than the vanilla API.

There are a few DOM libraries for JavaScript. They make it easier to manipulate the structure and create content.

Native JavaScript comes with prototypal class system as opposed to classical one. Various solutions have emerged to make it easier to deal with it the classical manner.

Specific JavaScript based video players encapsulate HTML5 Video related concerns and make it easier to write cross-platform solutions.

JavaScript based audio libraries wrap various browser APIs into coherent wholes that are easier to use. Examples: audiolib.js, XAudioJS, SoundJS.

JavaScript based physics libraries make it possible for you to perform collision detection, rigid body and blob simulations. Sometimes they integrate with some other engine.

As you usually want to perform various operations on your JavaScript code before a release, a set ofbuild utilities have been created for this purpose. Examples: Grunt, Brunch.

There are a wide range of code editors available for JavaScript that have been written in the language itself. These run on the browser.

HTML5 applications leverage some specific JavaScript related technologies. These include Canvas, Audio and Web Workers. Here we list a good examples of HTML5 apps for inspiration.

JavaScript color libraries make it easier to manipulate colors and convert them from a colorspace to another.

JavaScript based image manipulation libraries rely usually on HTML5 Canvas and provide some specific operations. Examples: CamanJS, Pixastic.

JavaScript based HTML5 Canvas wrappers encapsulate the API and build on top of that. Usually this results in a neater syntax and new functionality.

JavaScript routing libraries make it easier to deal with URIs. They leverage HTML5 capabilities. Examples: OriginJS, URI.js.

A set of functional programming libraries extend JavaScript’s capabilities further in this regard and make it easier to program in this specific way. Examples: Underscore.js, Sugar.

Localization (i18n) and internationalization (l10n) JavaScript libraries allow you to adapt your application to work on new languages and cultures. Examples: i18n-js, Jed.

There are several utilities that make it easier to deal with asynchronous programming, control flow and events in JavaScript. Examples: Async, Step, q.

JavaScript has become a popular platform for setting up presentations. These libraries provide nice transitions and can be styled with CSS.

JavaScript based animation libraries usually encapsulate the complex CSS syntax into something easier to use and provide new functionality not available in pure CSS based solution.