The name D3 stands for Data-Driven Documents. Mike Bostock has been openly developing this powerful data visualization library since 2011. It helps you draw beautiful graphics by manipulating data without worrying too much about pixel positions, calculating where things fit on a graph, and so on. If you've ever visualized data in Python or similar languages, you've probably used something similar to gnuplot . I assure you that d3.js offers a much more pleasurable experience.

The official website, d3js.org, features many great examples that show off the power of d3.js, but understanding them is tricky at best. After finishing this book, you should be able to understand d3.js well enough to figure out the examples. If you want to follow the development of d3.js more closely, the source code is hosted on GitHub at https://github.com/mbostock/d3.

The fine-grained control and its elegance make d3.js one of the most, if not the most, powerful open source visualization libraries out there. This also means that it's not very suitable for simple jobs such as drawing a chart or two—in that case you might want to use a library designed for charting. Many use d3.js internally anyway.

As a data manipulation library, d3.js is based on functional programming principles, which is probably where a lot of the confusion stems from. Unfortunately, functional programming goes beyond the scope of this book, but I'll explain all the relevant bits to make sure everyone's on the same page.