Learn how and why we build nearly all our components responsively and with base and modifier classes.
Bootstrap’s components are largely built with a base-modifier nomenclature. We group as many shared properties as possible into a base class, like .btn, and then group individual styles for each variant into modifier classes, like .btn-primary or .btn-success.
To build our modifier classes, we use Sass’s @each loops to iterate over a Sass map. This is especially helpful for generating variants of a component by our $theme-colors and creating responsive variants f or each breakpoint. As you customize these Sass maps and recompile, you’ll automatically see your changes reflected in these loops.
Check out our Sass maps and loops docs for how to customize these loops and extend Bootstrap’s base-modifier approach to your own code.