monster.js

 show_autocomplete: function (itemName, collection) {
      var accentMap = {
        "á": "a",
        "é": "e",
        "í": "i",
        "ó": "o",
        "ú": "u",
        "ñ": "n"
      };

      var normalize = function( term ) {
        var ret = "";
        for ( var i = 0; i < term.length; i++ ) {
          ret += accentMap[ term.charAt(i) ] || term.charAt(i);
        }
        return ret;
      };

      $('.' + itemName).autocomplete({
        source: function (request, response) {
          var contains1, containsMatcher1, startsWith1, startsWithMatcher1, term;
          term = normalize($.ui.autocomplete.escapeRegex(request.term));
          startsWithMatcher1 = new RegExp('^' + term, 'i');
          startsWith1 = $.grep(collection, function (value) {
            return startsWithMatcher1.test(value.label || value.value || value);
          });
          containsMatcher1 = new RegExp('\\b' + term, 'i');
          contains1 = $.grep(collection, function (value) {
            return $.inArray(value, startsWith1) < 0 && containsMatcher1.test(value.label || value.value || value);
          });
          return response(startsWith1.concat(contains1));
        }
      });
    }