Book Image

D3.js 4.x Data Visualization - Third Edition

By : Aendrew Rininsland, Swizec Teller
Book Image

D3.js 4.x Data Visualization - Third Edition

By: Aendrew Rininsland, Swizec Teller

Overview of this book

Want to get started with impressive interactive visualizations and implement them in your daily tasks? This book offers the perfect solution-D3.js. It has emerged as the most popular tool for data visualization. This book will teach you how to implement the features of the latest version of D3 while writing JavaScript using the newest tools and technique You will start by setting up the D3 environment and making your first basic bar chart. You will then build stunning SVG and Canvas-based data visualizations while writing testable, extensible code,as accurate and informative as it is visually stimulating. Step-by-step examples walk you through creating, integrating, and debugging different types of visualization and will have you building basic visualizations (such as bar, line, and scatter graphs) in no time. By the end of this book, you will have mastered the techniques necessary to successfully visualize data and will be ready to use D3 to transform any data into an engaging and sophisticated visualization.
Table of Contents (18 chapters)
Title Page
About the Authors
About the Author2
About the Reviewer
Customer Feedback
Shape Primitives of D3

All aboard the Koa train to servertown!

Okay, let's get into the nitty-gritty right away, and I'll explain what's going on. Add all of this into a new file in lib/chapter8 called index.js:

import * as Koa from 'koa';
import * as bodyParser from 'koa-bodyparser';
const app = new Koa();
const port = process.env.PORT || 5555;
app.listen(port, () => console.log(`Listening on port ${port}`));
export default app;

Here, we import Koa and Koa Body Parser, instantiate Koa, assign a port number (defaulting to 5555), tell Koa to use the Body Parser middleware (which mainly just interprets POST request bodies into JavaScript objects for us) and then tell Koa to listen on that port.

What is process.env.PORT? The process.env is simply a global object of all environment variables from the shell that spawned the NodeJS script. We listen for requests on either port 5555 or whatever the PORT environment variable is set to. I've emphasized that last line because it...