I have quite a bit of experience building webapps in ClojureScript. I was the main author of CircleCI's cljs frontend and I cofounded PrecursorApp, a collaborative prototyping app with a cljs frontend. Both codebases are open-source on GitHub (circleci/frontend and PrecursorApp/precursor).I wish I would have had this book when I started working with ClojureScript. ClojureScript has one of the best developer experiences, with code-reloading and a REPL, but it can be a bit daunting to set it up the first time. This book takes you through all the steps and keeps you from missing out on some of the best aspects of developing with ClojureScript.The second and third chapters might be a bit too much to take in at once for people new to ClojureScript. I'd recommend you skim them the first time, then come back and use them as a reference when you start building your application.The rest of the book gives you a nice foundation for building applications in ClojureScript. I may have focused on a few different libraries, but the ones they cover are pretty solid, with one notable exception. I wouldn't recommend anybody use Dommy. I used it and found it very confusing--you're much better off using the tools you get for free from Google Closure.There's lots of other great stuff in the book. I'll definitely be coming back to the section on ClojureScript modules--Precursor ships with a 1.5mb (only 388k gzipped) javascript file and I'd love to get that down to a more reasonable size.

In case you are even vaguely curious about ClojureScript and are wondering whether or not to learn it, I strongly encourage you to do so, as it has become obvious to me that it is the future of front-end web development. (Technically, it is one of several futures, but as it stands it has several years head start over most options except for CoffeeScript and of course native JavaScript. I have never programmed in CoffeeScript but having around 15 years experience with JavaScript I can safely tell you that ClojureScript provides a great many benefits to any programmer over JS, and that is even taking into account ES6 which does introduce a few of the benefits that have been native to ClojureScript since its inception.)I have been programming in ClojureScript for over a year now, and this book, which I bought last Christmas (directly in the Packt sale for a mere $5) helped my learning curve tremendously.The most important first step in learning any new language is setting up your development environment, and this book does an excellent job in covering this for ClojureScript. While it goes through a number of different scenarios, and this can seem confusing at first, by far the best option is to use Figwheel, which provides an as close to real-time live encoding flow as you are going to get for a compile-to-JS language.It also covers setting up Emacs as an IDE, which is probably at the very least the best editor (rather than IDE) available for programming in LISP dialects (of which ClojureScript is one), mostly due its paredit plugin. (I am much more of a Vim user but sadly I haven't found any plugin in Vim which comes close to the functionality that the emacs paredit plugin provides.)Chapters 2 and 3 cover the language fundamentals and some advanced features, including interop with JS and macros. The treatment of macros is adequate enough, however some more could have been written about them. Essentially, they allow you to write ClojureScript code which is rewritten, via macros, into some other ClojureScript code, which is ultimately compiled into JS. This is one of the most powerful features of the language, and once you have more experience with the language you will definitely want to write macros in certain situations where it makes sense.One area which is not covered adequately by the book is the ClojureScript and Clojure library core.async. This provides an amazing alternative way of handling events to that which is native to JS / the DOM. While events are still present when using core.async, event handlers become much more lightweight and the majority of event handling code is sent of to something known as a "go channel" which takes care of the bulk of work required, including any state management. There are a couple of excellent videos, one on youtube and one on Cognitect's website (entitles "core.async webinar") which show you some of the amazing things which you can achieve using core.async.Chapter 4 covers a decent selection of libraries which allow you to work with the DOM and do general web development, all of which are worth looking at if you are not using React.Chapter 5 covers React development, and herein is another major flaw of the book. There are several ClojureScript libraries available for working with React, and the book's authors chose to go with Om. I tried using Om following the guidelines in this book, together with the first two tutorials on the Om github page, and to cut a long story short, I couldn't get it to do what simple things I was trying to achieve. I found myself having to bend over backwards to fit my ideas into the Om framework, and after much hair-pulling, I gave up.Instead, I discovered Reagent, which is an amazing framework for building React applications using ClojureScript, not least of all because it is incredibly simple to use. I have been using Reagent for several months now and I have absolutely zero complaints, in short, it is an amazing framework and I cannot recommend it enough.Beyond this I have only read the section on testing, which again covers testing using the native cljs.test library more than adequately enough. However you should be aware that the developer of Figwheel created something called Devcards, which is designed primarily to test React components outside of their native application contexts, but also includes thorough testing capabilities which reports results in your browser rather than in a command-line session. If you search the web for "TDD in ClojureScript" you will find an article by Eric Smith which explains how to do this, it's well worth going through it all for the benefits you'll get.This is by far the best book available on ClojureScript at this time (there are only 3 others and one of those only covers Reagent), and I would highly recommend anyone starting out or with just a couple of month's experience in ClojureScript to read it and learn from it, it provides an incredibly invaluable resource to what I consider to be the most useful language for front-end web-development today.

This is a great and thorough introduction to ClojureScript. It makes no assumptions on what you may already know. Instead it focuses on building a strong foundation of knowledge. Two whole chapters are focused on just making sure you have a strong understanding of what ClojureScript is and what makes it different from JavaScript. That was invaluable as I went further into the book. From there the book teaches how to create a web application with React by way of Om. And rather than leave me high and dry with just a fun toy application the book wraps things up by teaching how to move code to a production environment. Definitely a strong recommend if you're interested in going from a ClojureScript beginner to a pro!

Pros :- Start from the basics and go through complex cases- Well written, can be seriously read in a 2/3 days period (if you have a little experience in clojure(script)- RecentCons:- Code examples in chapter 5 (om todo app with back-end) - some mistakes in code

A very clear introduction to developing with Clojurescript. The pacing was excellent. The examples made a ton of sense. I really liked how the author included links and tips to upcoming tech as well (such as the js compiler.)