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;

        };