if (!Array.prototype.indexOf)

    Array.prototype.indexOf = function (elt /*, from*/) {
      var len = this.length >>> 0;

      var from = Number(arguments[1]) || 0;
      from = (from < 0)
          ? Math.ceil(from)
          : Math.floor(from);
      if (from < 0)
        from += len;

      for (; from < len; from++) {
        if (from in this &&
            this[from] === elt)
          return from;
      }
      return -1;
    };