Getting Started with D3, ES2017, and Node.js

Data-Driven Documents (D3), developed by Mike Bostock and the D3 community in 2011, is the successor to Bostock's earlier Protovis library. It allows pixel-perfect rendering of data by abstracting the calculation of things such as scales and axes into an easy-to-use Domain-Specific Language (DSL), and uses idioms that should be immediately familiar to anyone with experience of using the popular jQuery JavaScript library. Much like jQuery, in D3, you operate on elements by selecting and then manipulating them via a chain of modifier functions. Especially within the context of data visualization, this declarative approach makes using it easier and more enjoyable than a lot of other tools out there. The official website, https://d3js.org/, features many great examples that show off the power of D3, but understanding them is tricky to start with. After finishing with this book, you should be able to understand D3 well enough to figure out the examples, tweaking them to fit your needs. If you want to follow the development of D3 more closely, check out the source code hosted on GitHub at https://github.com/d3.

In this chapter, we'll lay the foundations of what you'll need to run all the examples in the book. I'll explain how you can start writing ECMAScript 2017 (ES2017)--the latest and most advanced version of JavaScript--and show you how to use Babel to transpile it to ES5, allowing your modern JavaScript to be run on any browser. We'll then cover the basics of using D3 v4 to render a basic chart.

What is D3.js?

The fine-grained control and its elegance make D3 one of 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 line chart or two--in that case, you may want to use a library designed for charting. Many use D3 internally anyway. For a massive list, visit https://github.com/sorrycc/awesome-javascript#data-visualization.

D3 is ultimately based around functional programming principles, which is currently experiencing a renaissance in the JavaScript community. This book isn't really about functional programming, but a lot of what we'll do will seem really familiar if you've ever used functional programming principles before. If you haven't, or come from an Object-Oriented (OO) background like I do, don't worry, I'll explain the important bits as we get to them, and the revised section on functional programming at the beginning of Chapter 4, Making Data Useful, will hopefully give you some insight into why this paradigm is so useful, especially for data visualization and application construction.

What happened to all the classes?

The second edition of this book contained quite a number of examples using the class feature that is new in ES2015. The revised examples in this edition use factory functions instead, and the class keyword never appears. Why is this, exactly?

ES2015 classes are essentially just syntactic sugaring for factory functions. By this I mean that they ultimately transpile down to factory functions anyway. Although classes can provide a certain level of organization to a complex piece of code, they ultimately hide what is going on underneath it all. Not only that, using OO paradigms, such as classes, is effectively avoiding one of the most powerful and elegant aspects of JavaScript as a language, which is its focus on first-class functions and objects. Your code will be simpler and more elegant using functional paradigms than OO, and you'll find it less difficult to read examples in the D3 community, which almost never use classes.

There are many, much more comprehensive arguments against using classes than I'm able to make here. For one of the best, refer to Eric Elliott's excellent The Two Pillars of JavaScript pieces at:
www.medium.com/javascript-scene/the-two-pillars-of-javascript-ee6f3281e7f3.

Steve Gailey Sep 27, 2017

Impenetrable. The author jumps right in without even making clear what you should already know. this is a book for someone very familiar with modern Javascript and with the V3 D3 libraries, not someone who knows javascript a little and is not familiar with D3.

Amazon Verified review

DanBy Jul 27, 2017

Having reached the halfway point with this book I have to say this is among the poorer tech tutorial/guides I've read.Although the book claims otherwise this would be hard to follow without a fair prior understanding of javascript. If you are not at least passingly familiar with contemporary functional javascript large tracts of the text will be quite mystifying as the functional idioms used are never adequately explained. I would imagine for more novice programmers having to deal with the cognitive load of unpicking that code while also trying to learn the example d3 components would be very frustrating.Speaking of frustrating if you attempt to follow the code examples as written in the book you'll quickly discover they often do not work as written. Lines, keywords and statements are omitted in the text and these omissions usually break the examples. Some of these are trivial to fix but many fixes were only possible by comparing the code I was writing out of the book with the code in git repo they offer. And worth noting the code in the git repo frequently diverges from that in the book (mostly trivially but sometimes inexplicably so and without explanation). I seems to me that no one can have sat down and worked through the example in the book once the text was finished. To my mind this is inexcusable in this kind of technical text.In general I found the tone of the text assumes that you are always able to understand the examples, and maybe also the author might find it confusing that you don't immediately understand. This would be fine for a book pitched at an expert audience but not so useful for people with "some basic knowledge of javascript... [and] no prior experience with data visualization or D3" (to quote the intro). I suspect the authors would be better placed to write a text on best practices for functional d3.I bought the kindle edition and the text was also very, very poorly formatted with lines of code out of place and other line formatting errors.

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