D3 3.x, HTML, CSS, JavaScript
No-Library (pure JS), HTML, CSS, JavaScript
Slightly modified code from multiBar example at http://nvd3.org/livecode/#codemirrorNav to demonstrate defaulting to stacked bar.
ordinal scale
http://www.codewars.com/kata/53f9ee9f64b19d4b1d0001ed/train/javascript
https://www.codeeval.com/open_challenges/61/