CoffeeScript: Accelerated JavaScript Development

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CoffeeScript Accelerated JavaScript Development

For decades, programmers have written computer code in one language, and then programmatically translated that code into another, lower-level form (typically machine code that can be run directly by a microprocessor, or some sort of bytecode that can be interpreted by a virtual machine). For instance, source code written in C or C++ is compiled and assembled into machine code. In web programming, there are emerging languages and other tools for translating code into JavaScript. For instance, Google Web Toolkit allows the programmer to create web apps in Java. The latest addition to this category is CoffeeScript, a language that can be compiled into JavaScript, and is intended to reduce source code size and clutter by incorporating some of the best operators from other Web scripting languages, particularly Ruby. It is also the topic of a new tutorial, CoffeeScript: Accelerated JavaScript Development.

This book is authored by Trevor Burnham, who is credited as one of the early contributors to the project by Jeremy Ashkenas (the creator and project lead of CoffeeScript) in his foreword to the book. Published by Pragmatic Bookshelf on 3 August 2011, under the ISBN 978-1934356784, CoffeeScript: Accelerated JavaScript Development fills only 138 pages, which is certainly a change of pace from the majority of programming tomes now being released. This book's material is grouped into six chapters, plus four appendices — aside from a preface, which introduces CoffeeScript as well as a word game, which is used as the example project throughout the book. Oddly enough, the preface mentions jQuery, but not as one of the well-known attempts to streamline JavaScript code.

The first chapter, "Getting Started", begins by briefly explaining how to install Node and npm (Node Package Manager). These instructions assume that you are following along in a Linux environment or some emulation thereof. They also seem to assume that nothing goes wrong in any of the steps, because no troubleshooting guidance or references are provided. Given the number of moving parts required to get CoffeeScript running, as well as the technical pitfalls that could ensnare a Windows or Mac user, the author should have provided more clear and detailed installation instructions. Also, readers unfamiliar with Linux/Unix may be puzzled by some of the instructions. For instance, page 3 appears to state that the way to check that those two aforesaid packages are on your path, is to simply type in "PATH" (whereas what is needed is "echo $PATH"). From that point forward, the narrative gradually becomes more opaque, with cursory coverage of text editor plugins, the "coffee" command line compiler, REPL, "the soak" (an existential chain operator), and the limitations of trying to debug CoffeeScript code. It is quite possible that by the end of this chapter, many readers will decide to not bother trying to learn CoffeeScript, and instead to stick with plain JavaScript, possibly supplemented with jQuery (which is not to say that jQuery code is any easier to read).

In the next three chapters, the author presents the basics of CoffeeScript, including how to: define and use functions and their arguments; test conditionals; throw and catch exceptions; understand variable scoping and context; create arrays using splats; accept input from the console; create objects, arrays, and soaks (in more detail than before); iterate over collections; match patterns; define namespaces using modules; and create prototypes and classes. He makes extensive use of examples, which thankfully are concise (unlike some programming books whose example code span far too many lines, and sometimes even multiple pages — forcing the reader to dig through the code, trying to find the important lines). Also, the brevity of CoffeeScript syntax is undoubtedly a factor. However, his concise style extends to the narrative as well, and will likely cause newbies to have to read the material several times — and even then wonder whether they fully grasp the concepts. It seems that the author understands CoffeeScript extremely well, but is not always able to communicate that knowledge to the reader in a patient and comprehensible manner.

Chapter 5 is a primer on jQuery, and is apparently included in the book so that the example application (the word game) can be made to work in a web browser — since none of the code or narrative (aside from the example app) appears to be related to CoffeeScript. It would have been more efficient to simply point the reader to an online jQuery tutorial, and then present only the CoffeeScript-specific differences — or just briefly explain how to load CoffeeScript files in an HTML file, which could have been done in a sidebar. The last chapter demonstrates how to run CoffeeScript on a web server, utilizing Node.js, and also explores how the lack of threads in JavaScript can impact Node programming. The example project is made multiplayer using Node, Connect, and WebSocket.

The appendices provide answers to the end-of-chapter exercises, alternative methods of running CoffeeScript code, a JavaScript cheat sheet, and a list of a half dozen bibliographic references. This book concludes with a suspiciously-short index, at less than three pages long, which appears to provide only the first or earliest occurrences of the major terms. Consequently, anyone who tries to use this book as a reference work for looking up key terms quickly — or for finding their later occurrences — will likely need to obtain an electronic version of the book, since all e-readers have search functionality. Furthermore, the index is missing some key terms used in the text, such as "function callbacks" and "arbitrary expressions" — heck, it's even missing "expressions", a fundamental concept in any programming language.

Prospective readers who wish to learn more about the book, can visit Pragmatic Bookshelf's page, which offers brief descriptions of the book and its author — as does O'Reilly Media's page. But, as of this writing, only the former makes available an e-book version, pre-publication reader comments, a discussion forum, the example source code used in the book, and a link to a page for reporting errata, which already has more than half a dozen items listed. More are present in the text: "add [a] multiplayer capability" (page xx); a lone ")" missing its matching "(" (in Exercise 6, page 34); "in a lot in functions" (page 107; should read "in a lot of functions"); "a[n] overhead" (page 110); "everyone and their dog is" (page 116).

The author's writing style is sometimes quirky, which in most cases adds a bit of levity, but occasionally leads to the misuse of terms, e.g., array ranges usage described as "fantastical" (page 43). "BDFL" (page xiii) will prove puzzling at first to most readers. On page xvi, the reader is told that JavaScript "contains multitudes." — multitudes of what? And nothing can excuse the groan-inducing "automagically" (page 100).

In terms of the ordering of the topics, one of the most exasperating aspects of this book is the way that many language concepts — such as chained comparisons, and variables being true or false (or "truthy" or "falsy") — are not presented up front, on their own, but mixed in with discussions of other topics, including development of the game application, and even in the answers to the chapter questions (Appendix 1). This makes the book generally unsuitable as a reference, especially when combined with a disappointing index.

One might assume that the modest size of this book is a result of the small size of the language itself. But another factor is surely the pithy presentation style for even some of the most important concepts in the language. Perhaps worst of all — especially from the perspective of someone relatively new to programming — some basic concepts are not addressed, or the example code does not address common use cases. For instance, in CoffeeScript, how does one create a block consisting of multiple lines of code? On page 17, indentation is briefly mentioned, but the sample code shows single-line blocks only. Other important ideas are "saved as an exercise" (which may induce flashbacks to exasperating technical college textbooks). Some readers may conclude that the author didn't want to make the effort of fully describing the language, in a more canonical fashion, which would have resulted in a much longer, but more valuable book.

It is unclear as to how much of the likely mystification and frustration of the average reader will be due to the writing choices made by the author, and how much can be blamed on the sometimes cryptic syntax of CoffeeScript, evident in the discussion of topics such as function binding (Chapter 2) and keywords (e.g., from page 106, "what.x and @x are, of course, equivalent if and only if what is this." Of course!). Readers are told in the introduction that they do not need to be experts in JavaScript to understand the book's material, and can be amateurs (page xviii). But there are several places in the book where intermediate-level knowledge, at a minimum, would be needed. That sort of difficult material may be another point in the CoffeeScript journey where some readers will decide to eschew learning the language.

The production quality of the book is fine, except that the chosen font's ratio of height to width is more than what is usually found in books nowadays; when combined with inadequate spacing among the words within many of the sentences, it makes it difficult for the reader to rapidly scan the material. The e-book version reflects the same minor problem. Yet it makes excellent use of color for syntactically highlighting the code — a feature not seen in the print version.

So if you would like to do some JavaScript programming, but without writing any JavaScript, then one possible place to start your journey is CoffeeScript: Accelerated JavaScript Development. As of this writing, it is the only CoffeeScript book on the market. Yet should the language continue growing in popularity, then more substantial and recommendable books will probably become available.

Copyright © 2011 Michael J. Ross. All rights reserved.
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