var chap_array = new Array(
["Ai Girl 7",'ai-girl-7'],
["Ai Girl 6",'ai-girl-6'],
["Ai Girl 5",'ai-girl-5'],
["Ai Girl 4",'ai-girl-4'],
["Ai Girl 3",'ai-girl-3'],
["Ai Girl 2",'ai-girl-2'],
["Ai Girl 1",'ai-girl-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]);
}