var chapter_list = new Array(
  ["Vol.01 Ch.001","v01/c001"],
  ["Vol.01 Ch.002","v01/c002"],
  ["Vol.01 Ch.003","v01/c003"],
  ["Vol.01 Ch.004","v01/c004"],
  ["Vol.01 Ch.005.5: Like, Like, Love","v01/c005.5"],
  ["Vol.03 Ch.001: vol.03","v03/c001"],
  ["Vol.ES Ch.001: Extra 1","vES/c001"],
  ["Vol.ES Ch.002: Extra 2","vES/c002"],
  ["Vol.ES Ch.003: Extra 3","vES/c003"],
  ["Vol.ES Ch.004: Extra 4","vES/c004"],
  ["Vol.ES Ch.005: Extra 5","vES/c005"]
);

var total_chapters = 11;

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;