CLI app with ClojureScript on Node

README.md

First install clojure so the clj command will be available.

brew install clojure

Clone and move core.cljs to the right directory:

git clone https://gist.github.com/a6427534ea76cd4e9222a76eb398b289.git inc
cd inc
mkdir -p src/inc
mv core.cljs src/inc

To develop:

clj -m cljs.main --repl-env node
cljs.user=> (require '[inc.core])
cljs.user=> (inc.core/handle-input "1")
2
nil
;; change something in src/inc/core.cljs
cljs.user=> (require '[inc.core] :reload)
;; try the change

To compile the final output:

clj -m cljs.main --target node --output-to inc.js -O simple -c inc.core
chmod +x inc.js

Let's try!

$ time echo 1 | ./inc.js
2
echo 1  0.00s user 0.00s system 38% cpu 0.002 total
./inc.js  0.13s user 0.03s system 94% cpu 0.173 total

$ time ./inc.js 1
2
./inc.js 1  0.13s user 0.03s system 96% cpu 0.168 total

$ ./inc.js hello
Not a number: hello

$ echo $?
1

Yay.

core.cljs

(ns inc.core)

(def std-input (atom ""))

(defn handle-input
  [s]
  (let [n (js/parseFloat s)]
    (if (js/isNaN n)
      (do (println "Not a number:" s)
          (js/process.exit 1))
      (println (inc n)))))

(defn -main [& args]
  (if-let [s (first args)]
    (handle-input s)
    (do
      (.setEncoding js/process.stdin "utf8")
      (.on js/process.stdin "data"
           (fn [data]
             (swap! std-input #(str % data))))
      (.on js/process.stdin "end"
           (fn []
             (swap! std-input (fn [s]
                                (subs s 0 (dec (count s)))))
             (handle-input @std-input))))))

(set! cljs.core/*main-cli-fn* -main)

deps.edn

{:deps
 {org.clojure/clojurescript {:git/url "https://github.com/clojure/clojurescript.git"
                             :sha "2f233d633f6dc44823105fd544685fc4da43ac6c"}}
}