javascript implementation

README.markdown

@@ -23,8 +23,11 @@ This repo is a collection of implementations of the roman numeral kata in differ
 ## java
 * java 1.6.0.17 that comes with MacOSX 10.6.5. Any Java version will probably work fine.
 
+## javascript
+* `sudo brew install node`
+
 ## ruby 
 * 1.9.2 instaled with rvm - should probably run with 1.8 as well
 
 ## scala
-* java 1.6, Scala 2.9.0 and SBT 0.7.7
+* java 1.6, Scala 2.9.0 and SBT 0.7.7

javascript/numeral_to_roman

@@ -0,0 +1,2 @@
+#!/bin/bash
+node numeral_to_roman.js $1

javascript/numeral_to_roman.js

@@ -0,0 +1,44 @@
+var times = function(c, count){
+  result = ''
+  for (i = 0; i < count; i++){
+    result += c
+  }
+  return result;
+}
+
+var singular_number = function(number, ones_sign, fives_sign, tens_sign){
+  switch(number){
+    case 0:
+      return ''
+    case 1:
+    case 2:
+    case 3:
+      return times(ones_sign, number)
+    case 4:
+      return ones_sign + fives_sign
+    case 5:
+      return fives_sign
+    case 6:
+    case 7:
+    case 8:
+      return fives_sign + times( ones_sign, number - 5 )
+    case 9:
+      return ones_sign + tens_sign
+  }
+}
+
+var numeral_to_roman = function(number){
+  var thousands = Math.floor(number / 1000) % 10
+  var hundreds  = Math.floor(number / 100 ) % 10
+  var tens      = Math.floor(number / 10  ) % 10
+  var ones      = number % 10
+
+  var roman_thousands = times('M', thousands)
+  var roman_hundreds  = singular_number( hundreds, 'C', 'D', 'M')
+  var roman_tens      = singular_number( tens,     'X', 'L', 'C')
+  var roman_ones      = singular_number( ones,     'I', 'V', 'X')
+
+  console.log('' + roman_thousands + roman_hundreds + roman_tens + roman_ones)
+}
+
+numeral_to_roman(process.argv[2]);