var chapter_list = new Array(
  ["Vol.01 Ch.001: Choumaru","v01/c001"],
  ["Vol.01 Ch.002: Angel","v01/c002"],
  ["Vol.01 Ch.003: Rocker Motion","v01/c003"],
  ["Vol.01 Ch.004: May Be Blue","v01/c004"],
  ["Vol.01 Ch.005: The Cherry Blossoms Bloom","v01/c005"],
  ["Vol.02 Ch.001: Scene 1","v02/c001"],
  ["Vol.02 Ch.002: Scene 2","v02/c002"],
  ["Vol.02 Ch.003: Scene 3","v02/c003"],
  ["Vol.02 Ch.004: Scent Last","v02/c004"],
  ["Vol.02 Ch.005: Born","v02/c005"]
);

var total_chapters = 10;

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;