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Hello, ClojureScript! (with jQuery)

· Java Zone

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I was looking for something really minimal, and the first simple example on my Google search was Daniel Harper’s article. I got rid of noir, used up to date versions of libraries, and voila – it’s working!

When I had my first “hello world” alert showing on page load, I decided to make things a little bit more interesting and introduce jQuery. I found jayq from Chris Granger and decided to give it a shot. There’s also a sample app on Chris’ blog that helped me with some issues, namely figuring out how to bind events. It references a few more interesting libs (namely fetch & crate), but I’ve had enough for now. I guess I could spend the whole night chasing such references.

In the end, the interesting pieces of code are below:

project.clj (configured to compile CLJS from src-cljs to resources/public/js/cljs.js):

(defproject hello-clojurescript "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.4.0"]
                 [ring "1.1.6"]
                 [jayq "0.1.0-alpha3"]]
  :plugins [[lein-cljsbuild "0.2.8"]]
   :source-path "src-cljs"
    :output-to "resources/public/js/cljs.js"
    :optimizations :simple
    :pretty-print true
  :main hello-clojurescript.core

core.clj (trivial app, with Ring wrapper configured to serve JS resources):

(ns hello-clojurescript.core
  (:require [ring.adapter.jetty :as jetty]
            [ring.middleware.resource :as resources]))
(defn handler [request]
  {:status 200
   :headers {"Content-Type" "text/html"}
   (str "<!DOCTYPE html>"
        "<p id=\"clickable\">Click me!</p>"
        "<p id=\"toggle\">Toggle Visible</p>"
        "<script src=\"http://code.jquery.com/jquery-1.8.2.min.js\"></script>"
        "<script src=\"js/cljs.js\"></script>"
(def app
  (-> handler
    (resources/wrap-resource "public")))
(defn -main [& args]
  (jetty/run-jetty app {:port 3000}))

hello-clojurescript.cljs (this one gets compiled to JavaScript):

(ns hello-clojurescript
  (:use [jayq.core :only [$ delegate toggle]]))
(def $body ($ :body))
(delegate $body :#clickable :click
          (fn [e]
            (toggle ($ :#toggle))))

Complete source code with instructions can be found at my GitHub repository.

At the moment I see the following issues:

  • I’m really green at ClojureScript. Tons to learn here!
  • The JavaScript file compiled from this trivial example is 13k lines long and weighs about 500 kb. Doh! Fine for local development on desktop, not that good for targetting mobile.
  • The official docs for ClojureScript are really… discouraging. Just like core Clojure documentation, they are pretty academic and obscure.
  • Docs for jayq are… Wait a minute, nonexistent? At least it’s a fairly thin adapter with small, comprehensible codebase.




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