AR Script: reversed image sequence

    var reNumber = /(.+?)(\d{1,4})/;
    extractedFilename = reNumber.exec(item.newBasename);
    return extractedFilename[1] + zpad((app.itemCount * 2 + 1 - index).toString(), 3);

function zpad(str, nb_digits) {
    if (str.length < nb_digits)     { return (Array(nb_digits - str.length + 1).join('0') + str); }
    else                            { return str; }
}