Fixing problem with negative ordinals.

This commit resolves #15

Author: marlun78

spec/toOrdinalSpec.js

@@ -4,6 +4,12 @@ var toOrdinal = typeof require !== 'undefined' ? require('../src/toOrdinal') : w
 
 describe('toOrdinal', function () {
     var tests = [
+        { input: -121, expect: '-121st' },
+        { input: -13, expect: '-13th' },
+        { input: -12, expect: '-12th' },
+        { input: -11, expect: '-11th' },
+        { input: -3, expect: '-3rd' },
+        { input: -2, expect: '-2nd' },
         { input: -1, expect: '-1st' },
         { input: 0, expect: '0th' },
         { input: 1, expect: '1st' },

src/toOrdinal.js

@@ -13,7 +13,7 @@ function toOrdinal(number) {
     var num = parseInt(number, 10);
     if (!isFinite(num)) throw new TypeError('Not a finite number: ' + number + ' (' + typeof number + ')');
     var str = String(num);
-    var lastTwoDigits = num % 100;
+    var lastTwoDigits = Math.abs(num % 100);
     var betweenElevenAndThirteen = lastTwoDigits >= 11 && lastTwoDigits <= 13;
     var lastChar = str.charAt(str.length - 1);
     return str + (betweenElevenAndThirteen ? 'th'