An introduction to UI libraries

UI libraries, frameworks, and utilities are not essential. We could build any user interface (despite its complexity) from scratch using vanilla JavaScript, HTML, and CSS. Still, we would often find ourselves using the same patterns, accessibility rules, optimizations, and utility functions on every user interface we build. So here comes the concept of a UI library.

The idea is to abstract our most common use cases, reuse most of the code on different user interfaces, improve our productivity, and use well-known, tested, and themeable UI components.

With "themeable," we refer to those libraries and components that allow us to customize the color scheme, spacing, and the whole design language of a given framework.

We could take the popular Bootstrap library as an example. It allows us to override its default variables (such as colors, fonts, mixins, and so on) to customize the default theme. Thanks to that feature, we could potentially...