var chapter_list = new Array(
  ["Ch.001.1: Hanon","c001.1"],
  ["Ch.001.2: Hanon","c001.2"],
  ["Ch.002: Sonata","c002"],
  ["Ch.003: The Middle-Schooler From Next Door","c003"],
  ["Ch.004: Kono Koi no Daihon","c004"],
  ["Ch.005: A Person Very Different From Me","c005"]
);

var total_chapters = 6;

for (var i = 0; i < chapter_list.length; i++) {
  document.getElementById('top_chapter_list').options[i] = new Option(chapter_list[i][0], chapter_list[i][1]);
  document.getElementById('bottom_chapter_list').options[i] = new Option(chapter_list[i][0], chapter_list[i][1]);
}
document.getElementById('top_chapter_list').value=current_chapter;
document.getElementById('bottom_chapter_list').value=current_chapter;
var current_chapter_index = document.getElementById('top_chapter_list').selectedIndex;