var chap_array = new Array(
    ["18",'18/01'],

    ["17",'17/01'],

    ["16",'16/01'],

    ["15",'15/01'],

    ["14 - Secret Feelings",'14/01'],

    ["13 - Ikemen's Good Luck Charm",'13/01'],

    ["12",'12/01'],

    ["11 - Steps to Adulthood",'11/01'],

    ["10",'10/01'],

    ["9",'9/01'],

    ["8 - Dream Come True",'8/01'],

    ["7 - Birthday Present",'7/01'],

    ["6",'6/00-cover'],

    ["5",'5/01'],

    ["4",'4/01'],

    ["3",'3/01'],

    ["2",'2/01'],

    ["1",'1/001']
);
for (var i=0; i<chap_array.length; i++) {
    document.getElementById('id_chapter_1').options[i] = new Option(chap_array[i][0],chap_array[i][1]);
    if (document.getElementById('id_chapter_2')) {
        document.getElementById('id_chapter_2').options[i] = new Option(chap_array[i][0],chap_array[i][1]);
    }
}