var chapter_list = new Array(
  ["Vol.01 Ch.001.1: And So I Became Rich","v01/c001.1"],
  ["Vol.01 Ch.001.2: [continuation]","v01/c001.2"],
  ["Vol.01 Ch.001.3: [continuation]","v01/c001.3"],
  ["Vol.01 Ch.002.1: Only She Knows","v01/c002.1"],
  ["Vol.01 Ch.002.2: [continuation]","v01/c002.2"],
  ["Vol.01 Ch.003: The Reason They Are Here","v01/c003"],
  ["Vol.01 Ch.004: You Wanna Buy?","v01/c004"],
  ["Vol.02 Ch.005: Light and Shadow I","v02/c005"],
  ["Vol.02 Ch.006: Light and Shadow II","v02/c006"]
);

var total_chapters = 9;

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;