var chap_array = new Array(
    ["4 - For Today That I Don't Know, Thankyou",'4/01'],

    ["3 - Rain, Under Your Umbrella",'3/01'],

    ["2 - The Feeling Behind a Smile",'2/01'],

    ["1 - Danger Doki Doki",'1/00']
);
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]);
    }
}