var chap_array = new Array(
["Baka to Boin 6",'baka-to-boin-6'],
["Baka to Boin 5",'baka-to-boin-5'],
["Baka to Boin 4",'baka-to-boin-4'],
["Baka to Boin 3",'baka-to-boin-3'],
["Baka to Boin 2",'baka-to-boin-2'],
["Baka to Boin 1",'baka-to-boin-1']);

for (var i=0; i<chap_array.length; i++) {
document.getElementById('chapter_select').options[i] = new Option(chap_array[i][0],chap_array[i][1]);
}