Fix handling of decimal digits, following the authors style.

lib/index.js

@@ -2,10 +2,12 @@
  * Comma number formatter
  * @param {Number} number Number to format
  * @param {String} [separator=','] Value used to separate numbers
+ * @param {String} [decimalSeparator='.'] Value used to separate decimal digits
  * @returns {String} Comma formatted number
  */
-module.exports = function commaNumber (number, separator) {
+module.exports = function commaNumber (number, separator, decimalSeparator) {
   separator = typeof separator === 'undefined' ? ',' : ('' + separator)
+  decimalSeparator = typeof decimalSeparator === 'undefined' ? '.' : ('' + decimalSeparator)
 
   // Convert to number if it's a non-numeric value
   if (typeof number !== 'number') {
@@ -21,12 +23,21 @@ module.exports = function commaNumber (number, separator) {
   if (!isFinite(number)) {
     return '' + number
   }
+
+  var result = []
+
+  // Grab decimal part
+  var decimalString = ('' + number).split(decimalSeparator)[1]
+
+  if (decimalString) {
+    result[] = decimalSeparator + decimalString
+  }
 
-  var stringNumber = ('' + Math.abs(number))
+  // Process integer part
+  var stringNumber = ('' + Math.abs(Math.floor(number)))
     .split('')
     .reverse()
 
-  var result = []
   for (var i = 0; i < stringNumber.length; i++) {
     if (i && i % 3 === 0) {
       result.push(separator)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "comma-number",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "Format a number with commas",
   "main": "lib/index.js",
   "scripts": {

test/index.js

@@ -21,6 +21,14 @@ test('Formatting', function (t) {
     [-100000, '-100,000'],
     [-1000000, '-1,000,000'],
     [-Infinity, '-Infinity'],
+
+    // Decimal numbers
+    [-1.1, '-1.1'],
+    [-100.1, '-100.1'],
+    [-1000.1, '-1,000.1'],
+    [-10000.1, '-10,000.1'],
+    [-100000.1, '-100,000.1'],
+    [-1000000.1, '-1,000,000.1']
 
     // Strings
     ['0', '0'],