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Executing Javascript from Clojure

2015-Sep-25 06:58
clojurejavascript

If you want to execute Javascript from Clojure, one option is to use embedded Rhino or Nashorn instance . More details here:

ScriptEngineManager

Java generalizes all scripting language support through ScriptEngineManager class. Here's how you can use it in Clojure:

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(ns icyrock.script-engine-prb
  (:import [javax.script ScriptEngineManager])
  (:require [clojure.pprint :refer [pprint]]
            [clojure.string :refer [join]]))
 
(defn get-available-script-engines []
  (for [sef (-> (ScriptEngineManager.) .getEngineFactories)]
    {:engine-name (.getEngineName sef)
     :engine-version (.getEngineVersion sef)
     :language-name (.getLanguageName sef)
     :language-version (.getLanguageVersion sef)
     :mime-types (join ", " (.getMimeTypes sef))
     :names (.getNames sef)}))
 
(defn get-javascript-engine []
  (-> (ScriptEngineManager.)
      (.getEngineByMimeType "application/javascript")))
 
(def some-javascript
  "
function collatz(n) {
  var c = []
  for(; n > 1; n = n % 2 ? n * 3 + 1 : n / 2) {
    c.push(n)
  }
  c.push(1)
  return c
}
 
collatz(27).join(', ')
"
  )
 
(defn eval-some-javascript []
  (-> (get-javascript-engine)
      (.eval some-javascript)
      (println)))
 
(defn main []
  (pprint (get-available-script-engines))
  (eval-some-javascript))

Sample output:

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icyrock.script-engine-prb> (pprint (get-available-script-engines))
({:engine-name "Oracle Nashorn",
  :engine-version "1.8.0_40",
  :language-name "ECMAScript",
  :language-version "ECMA - 262 Edition 5.1",
  :mime-types
  "application/javascript, application/ecmascript, text/javascript, text/ecmascript",
  :names
  ["nashorn" "Nashorn" "js" "JS" "JavaScript" "javascript" "ECMAScript" "ecmascript"]})
nil
icyrock.script-engine-prb> (eval-some-javascript)
27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, 322, 161, 484, 242, 121, 364, 182, 91, 274, 137, 412, 206, 103, 310, 155, 466, 233, 700, 350, 175, 526, 263, 790, 395, 1186, 593, 1780, 890, 445, 1336, 668, 334, 167, 502, 251, 754, 377, 1132, 566, 283, 850, 425, 1276, 638, 319, 958, 479, 1438, 719, 2158, 1079, 3238, 1619, 4858, 2429, 7288, 3644, 1822, 911, 2734, 1367, 4102, 2051, 6154, 3077, 9232, 4616, 2308, 1154, 577, 1732, 866, 433, 1300, 650, 325, 976, 488, 244, 122, 61, 184, 92, 46, 23, 70, 35, 106, 53, 160, 80, 40, 20, 10, 5, 16, 8, 4, 2, 1
nil
icyrock.script-engine-prb>