If you've ever watched old sci-fi flicks, you know how powerful loops can be. Feed your robot nemesis an infinite loop, and kaboom. Robo dust.
Preprocessor loops will not cause dramatic explosions in space (I hope), but they are useful for writing DRY CSS. While everyone is talking about pattern libraries and modular design, most of the focus has been on CSS selectors. No matter what acronym drives your selectors (BEM, OOCSS, SMACSS, ETC), loops can help keep your patterns more readable and maintainable, baking them directly into your code.
We'll take a look at what loops can do, and how to use them in the major CSS preprocessors: Sass, Less, and Stylus. Each language provides a unique syntax, but they all get the job done. There's more than one way to loop a cat.