Modern ClojureScript

ATTENTION NOTE: I'm in the process of gradually updating the series. At the moment I updated the series up to the tutorial-07, while all the others are still using aged stuff. Please be patient because it will take at least a month to complete the work.

Modern ClojureScript (modern-cljs) is a series of tutorials that guide you in creating and running ClojureScript (CLJS) projects.

CLJS is a compiler for the Clojure programming language that targets JavaScript. It emits JavaScript code which runs in web browsers and other client-side or server-side JavaScript interpreters (e.g. nodejs).

Required background

These tutorials require that you have some prior programming experience. They assume you've gotten your hands dirty by trying a little Clojure, even if you're not proficient in it yet. It will also be quite helpful if you have some experience programming for the Web using HTML, JavaScript and the browser DOM.

If you don't know anything about Clojure (or about Lisp), I recommend you learn a little bit before starting these tutorials.

There are plenty of outstanding resources on Clojure that are freely available on the Internet, and you can't overestimate the benefit of reading a book on Clojure (or another Lisp dialect) to your value as a programmer.

Here are some book recommendations:

Clojure Programming: written by three of the heroes of Clojure, it contains everything you need to know about Clojure and its ecosystem.
Programming Clojure: written by another legendary Clojure developer, it's the easiest path to learning Clojure.
The Joy of Clojure: the title speaks by itself. A must read!
ClojureScript Up and Running: at the moment, it's the only published book on ClojureScript. Even though it's not old, the book is a bit outdated since ClojureScript is evolving quickly. It's brief and useful, especially if you want to integrate with external JavaScript libraries.
SICP - Structure and Interpretation of Computer Programs: this is the best programming book I've read in my very long career. It uses Scheme/Racket (a Lisp dialect) rather than Clojure and is available online, in print, or in a lecture series.
On Lisp: if you want to learn about macros, this is the place to start. It uses Common Lisp (a Lisp dialect) rather than Clojure.

Required tools

Many people worry about which operating system and editor/IDE are best for developing in Clojure and ClojureScript. I personally use Mac OS X, Debian and Ubuntu. I use Emacs as an editor.

Because I'm an old-timer, *nix and Emacs are the OS and editor I know best. That being said, in this series of tutorials you're not going to find any suggestions or reference to operating systems or editors. Use whatever tools you already have and know. I have too much respect for people developing IDE/plugins for Clojure/CLJS to say that one is better than another, and you don't want to combine learning a new programming language with trying to learn a new programming environment.

You will need to have git installed and you'll need some familiarity with the basics of git.

Why the name Modern ClojureScript?

You might wonder why this tutorial series is named modern-cljs when ClojureScript is so recent. I started this series while trying to port a few examples from the Modern JavaScript: Develop and Design book to ClojureScript, and now it's too late to change.

The Tutorials

Introduction

This series of tutorials guides you in creating and running simple CLJS projects. The bulk of the series follows the progressive enhancement of a single project.

While working through the tutorials I strongly suggest you start at tutorial 1 and type in all the code for each tutorial yourself. In my experience this is the the best approach if you're not already very fluent with the programming language.

Tutorial 1 - The Basics

Create and configure a very basic CLJS project.

Tutorial 2 - Browser CLJS REPL (bREPL)

Set up a browser-connected CLJS REPL (bRepl) using an external http-server.

Tutorial 3 - Ring and Compojure

Replace the external http-server with Ring, a Clojure HTTP server and middleware, and Compojure, a routing library for Ring.

Tutorial 4 - Modern ClojureScript

Have some fun with CLJS form validation by porting the JavaScript login form example from Modern JavaScript: Develop and Design to CLJS.

Tutorial 5 - Introducing Domina

Use the Domina library to make our login form validation more Clojure-ish.

Tutorial 6 - The Easy Made Complex, and the Simple Made Easy

Investigate and find two different ways to solve an issue from the last tutorial.

Tutorial 7 - Compilation Modes

Explore CLJS/CLS compilation modes by using the lein-cljsbuild plugin of leiningen, and discover a problem and solve it using a feature of the lein-cljsbuild plugin.

Tutorial 8 - Introducing Domina Events

Use Domina events for a more Clojure-ish approach to handing DOM events.

Tutorial 9 - DOM Manipulation

Programmatically manipulate DOM elements in response to DOM events.

Tutorial 10 - Introducing AJAX

Use AJAX to let the CLJS client-side code communicate with the server.

Tutorial 11 - A Deeper Understanding of Domina Events

Apply Domina events to the login form example from the 4th Tutorial.

Tutorial 12 - HTML on Top, Clojure on the Bottom

Explore the highest (HTML5) and deepest (Clojure on the server) layers of the login form example from the previous tutorial.

Tutorial 13 - Don't Repeat Yourself

Respect the Don't Repeat Yourself (DRY) principle by sharing validators between the client-side CLJS and the server-side Clojure.

Tutorial 14 - Better Safe Than Sorry (Part 1)

Set the stage for unit testing by learning about the Enlive template sytem and starting the shopping calculator example. Use code refactoring to satisfy the DRY principle and to solve a cyclic namespaces dependency problem.

Tutorial 15 - Better Safe Than Sorry (Part 2)

Add validators to the shoppingForm, and do some unit testing.

Tutorial 16 - Better Safe Than Sorry (Part 3)

Make our unit tests portable between Clojure and CLJS by using the clojurescript.test lib and the cljx lein plugin.

Tutorial 17 - REPLing with Enlive

Integrate the form validators from the server-side Shopping Calculator into the Web UI, so the user is notified with the right error messages when typing invalid values into the form.

Tutorial 18 - Housekeeping!

A digression to cover two topics on CLJS developer productivity: setting up a more comfortable browser REPL based on nREPL, and a more comfortable project structure using the profiles features of Leiningen.

Tutorial 19 - Livin' On the Edge

Learn how to contribute something we need to someone else's library, and how to publish snapshot releases on clojars to use the enhancement in our own project.

Tutorial 20 - Learning by Contributing (Part 1)

Look at the Enfocus library with the objective of sharing as much code as possible with Enlive. Start an open source collaboration by proposing a few improvements to the Enfocus directory structure and the adoption of the clojurescript.test library for implementing unit tests.

Tutorial 21 - Learning by Contributing (Part 2)

Package Enfocus into a jar, instrument it with the Piggieback library, publish it on clojars, and use it as a dependency in a very simple project to see that the changes we made don't affect the Enfocus codebase, which still works as expected.

Tutorial 22 - Learning by Contributing (Part 3)

Improve Enfocus by applying separation of concerns and implementing a few unit tests. In the process, discover some bugs and correct them by first interacting with Enfocus in the REPL.

dagolap/modern-cljs