We are now introducing the author's favorite library, a very powerful and cutting-edge visualization library for JavaScript called D3, standing for data-driven documents. D3 is the state of the art when it comes to creating custom interactive data visualizations in the web browser using SVG, HTML, and CSS, from basic ones such as bar or pie charts to more complex ones as well. It's important to note that D3 does not introduce new visual representations but solely makes use of existing ones and focuses exclusively on transforming them.

Before starting to describe the library in detail, it's paramount to understand some fundamentals around visual representations and why the library leverages SVGs to create data visualizations.