JavsScript word scrambler

scramble.js

      /* Called on document.ready */
      $(function () {
        $("body *").replaceText(/\b([A-z]{4,})\b/g, scramble_inner );
      });
      /* Scramble the inner characters of a word */
      function scramble_inner(word) {
        return word[0] 
          + force_shuffle(word.slice(1, word.length - 1))
          + word[word.length - 1];
      }
      /* Randomize characters in the string, but check to make sure
       * they're different from the original. Handle's the special
       * case where all inner characters are equal, for instance "moooo".
       */
      function force_shuffle(str) {
        if (all_chars_same(str)) return str;
        var result = str;
        while (str === result) {
          result = str.split('').sort(function() {
            return Math.floor(Math.random() * 2) ? 1 : -1;
          }).join('');
        }
        return result;
      }
      /* Check whether all characters in the string are equal, eg "ooo" */
      function all_chars_same(str) {
        for (i = 0; i < str.length; i++) {
          if (str[i] !== str[0]) {
            return false;
          }
        }
        return true;
      }