This chapter was all about tooling. We started with linting using ESLint, then moved up to static typing using TypeScript, then finished with some testing in Mocha. That's a lot of ground to cover! Don't feel bad if you're a bit overwhelmed by it all right now, this was meant to be a really shallow overview of these tools and how to use them with D3. There are lots of resources you can pursue now that you know the basics; I highly recommended reading a little more about testing because that's really probably the biggest and most important of all of them.
We will close this book by looking at some particularly impressive examples of data visualization. Don't worry, we're done with coding now; sit back, relax, and enjoy the show as we take a quick look at what makes for a quality data visualization.