JavaScript for Data Science

Maya Gans, Toby Hodges, Greg Wilson

• Publisher: Chapman and Hall/CRC
• Year: 2020
• Print ISBN: 9780367426521
• eBook ISBN: 9781000028591
• Topic: Informatica
• Subtopic: Informatica generale

JavaScript is the native language of the Internet. Originally created to make web pages more dynamic, it is now used for software projects of all kinds, including scientific visualization and data services. However, most data scientists have little or no experience with JavaScript, and most introductions to the language are written for people who want to build shopping carts rather than share maps of coral reefs.

This book will introduce you to JavaScript's power and idiosyncrasies and guide you through the key features of the language and its tools and libraries. The book places equal focus on client- and server-side programming, and shows readers how to create interactive web content, build and test data services, and visualize data in the browser. Topics include:

• The core features of modern JavaScript
• Creating templated web pages
• Making those pages interactive using React
• Data visualization using Vega-Lite
• Using Data-Forge to wrangle tabular data
• Building a data service with Express
• Unit testing with Mocha

All of the material is covered by the Creative Commons Attribution-Noncommercial 4.0 International license (CC-BY-NC-4.0) and is included in the book's companion website.

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Maya Gans is a freelance data scientist and front-end developer by way of quantitative biology. Toby Hodges is a bioinformatician turned community coordinator who works at the European Molecular Biology Laboratory. Greg Wilson co-founded Software Carpentry, and is now part of the education team at RStudio

1 Introduction

David Beazley¹ thought that “JavaScript versus Data Science” would be a better title for this book. While that one word sums up how many people view the language, we hope we can convince you that modern JavaScript is usable as well as useful. Scientists and engineers are who we were thinking of when we wrote this book but we hope that these lessons will also help librarians, digital humanists, and everyone else who uses computing in their research.

We will cover:

• Core features of modern JavaScript

• Programming with callbacks and promises

• Creating objects and classes

• Writing HTML and CSS

• Creating interactive pages with React

• Building data services

• Testing

• Data visualization

• Combining everything to create a three-tier web application

Unlike most introductions to JavaScript, these lessons present an even mix of browser programming and server programming. We give each topic only shallow coverage; if you want to know more, there are many other free tutorials you can dive into once you’ve mastered the basics, some of which are both up-to-date and well designed.

1.1 WHO YOU ARE

Every lesson should aim to meet the needs of specific learners² [Wils2019]. The three people described below define the intended audience for this one.

Bhadra received a BSc in microbiology five years ago, and has worked since then for a biotech firm with labs in four countries. She did a statistics class using R as an undergrad, then learned some more R and some Unix shell scripting in a Software Carpentry³ workshop, but has no other training as a programmer. Bhadra’s team is developing tools to detect structural similarities between proteins. They would like to build a browser interface to their tools so that people can test different algorithms on various datasets. This book will show Bhadra how to build, test, and deploy that interface.

Efraim did fieldwork for the Ministry of Natural Resources for thirty-one years. He learned Visual Basic so that he could write Excel macros, then mastered C in order to maintain the control software for some second-hand remote sensing equipment. Efraim recently retired, and is now an active member of several citizen science projects. This book will show him how to create a service to share those projects’ data with the world, and how to build a web-based administrative interface for it.

Sumi is completing a PhD in 19th Century history. As part of her research, she is transcribing and cataloging the records of several dozen Japanese-American midwives. She has been creating and customizing WordPress sites for several years, and has picked up bits and pieces of JavaScript while doing so. Sumi is about to start looking for a job, and wants to create an interactive website to showcase her research. This book will fill in some of the gaps in her knowledge and show her how to take advantage of JavaScript’s more modern features.

These prototypical users:

• can write two-page programs that use lists, loops, conditionals, and functions,

• can run commands in the Unix shell to navigate the filesystem and create and delete directories and files, and

• have reliable access to the Internet.

1.2 WHO WE ARE

Maya Gans is a freelance data scientist and front-end developer by way of quantitative biology. She has 4 years of experience programming in R, and her passion for data visualization brought her to the weird world of JavaScript. When she isn’t debugging or blogging⁴ about code, she’s somewhere remote climbing large mountains. She dedicates this book to her fellow self-taught programmers who were told they weren’t good enough but are too driven and excited to care.

Toby Hodges⁵ is a bioinformatician turned community coordinator, working on the Bio-IT Project⁶ at EMBL⁷. He teaches a lot of courses in computing, organizes a lot of community-building events, listens to a lot of punk rock, and occasionally still finds time to write code and ride his bike. Toby would like to thank his wife for her support and patience while he swore about how annoying JavaScript is to debug.

Greg Wilson⁸ has worked for 35 years in both industry and academia, and is the author or editor of several books on computing and two for children. He co-founded Software Carpentry⁹, a non-profit organization that teaches basic computing skills to researchers, and is now part of the education team at RStudio¹⁰. Greg would like to thank everyone at Rangle¹¹ who was so patient with him when he was learning JavaScript.

1.3 SETTING UP

You can find the examples for each chapter in the src directory in our GitHub repository¹². Each sub-folder contains the code and data needed to follow along with the text.

The exercises at the end of each chapter include new information that you will need later in the book, and are therefore not optional. You can do the first few online, using a service like RunKit¹³, which gives you an interactive JavaScript playground in your browser. For larger things, and for chapters starting with the one on creating dynamic web pages (Chapter 7), you should download and install¹⁴ the latest Longterm Support (LTS) versions of Node and NPM.

Node is an open source implementation of JavaScript that includes a command-line interpret...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Chapter 1 Introduction
• Chapter 2 Basic Features
• Chapter 3 Callbacks
• Chapter 4 Objects and Classes
• Chapter 5 HTML and CSS
• Chapter 6 Manipulating Pages
• Chapter 7 Dynamic Pages
• Chapter 8 Visualizing Data
• Chapter 9 Promises
• Chapter 10 Interactive Sites
• Chapter 11 Managing Data
• Chapter 12 Creating a Server
• Chapter 13 Testing
• Chapter 14 Using Data-Forge
• Chapter 15 Capstone Project
• Chapter 16 Finale
• Bibliography
• Appendix A License
• Appendix B Code of Conduct
• Appendix C Contributing
• Appendix D Glossary
• Appendix E Key Points
• Appendix F Collaborating
• Appendix G Legacy JavaScript Issues
• Appendix H Regular Expressions
• Appendix I Logging
• Appendix J Extensible Servers
• Appendix K Using a Database
• Appendix L Deploying
• Index