I've mentioned previously that D3 is very functionally designed, meaning that it uses some of the idioms JavaScript has adopted from functional programming. Although we can still approach D3 development in a very classical, object-oriented fashion, our lives will be much easier if we start thinking about our code and data with a functional mindset.
The good news is that JavaScript almost counts as a functional language; there are enough features to get the benefits of a functional style, and it also provides enough freedom to do things imperatively or in an object-oriented way. The bad news is that, unlike real functional languages, the environment gives no guarantee about our code.
Note
Later on, in Chapter 9, Having Confidence in Your Visualizations, we'll look at TypeScript, which allows compilation of JavaScript using static types, and Tern.JS , which analyzes code in order to improve tooling. These efforts go a great deal toward improving confidence in...