A playground for your html, css and javascript code. You can use this to create a small experimental code to test across all browsers. You can also share you code with others and work off others code (forking)
WARNING: Addictive games alert, if you want to stay productive, do not click on any of these links. :P Few years back, most of the online games were made with Flash, nowadays, with powerful browsers and web technologies, you can create games with just HTML, CSS and Javascript!
In the red corner, weighing in at just 29Kb (uncompressed), is knockout.js; a pure JavaScript library that simplifies the creation of dynamic user interfaces. Knockout is library agnostic, so it can easily be used with any of the most popular JavaScript libraries already available, but it works particularly well with jQuery, and uses jQuery.tmpl as its default templating engine.
This is an easy to understand article about the Promise pattern for Javascript. It is a way to have a 'continue with this function when this previous one succeeds' that doesn't involve nesting functions.
The jqXHR objects returned by $.ajax() as of jQuery 1.5 implement the Promise interface, giving them all the properties, methods, and behavior of a Promise.
A good tutorial on where you should define a function in javascript and why. Includes some major performances considerations. Basic takeaway: nested functions means tonnes of "identical" functions being creating.
Visibility.js allow you to determine whether your web page is visible to an user, is hidden in background tab or is prerendering. It allows you use the page visibility state in JavaScript logic and improve browser performance by disabling unnecessary timers and AJAX requests, or improve user interface experience (for example, by stopping video playback or slideshow when user switches to another browser tab).
Simple wrapper for cross-browser usage of the JavaScript Fullscreen API, which lets you bring the page or any element into fullscreen. Smoothens out the browser implementation differences, so you don't have too.