function select_all(e) {
  for(var i = 0; i < document.getElementById(e).elements.length; i++) {
    if(document.getElementById(e).elements[i].type == "checkbox")
      document.getElementById(e).elements[i].checked = true;
  }
}

function unselect_all(e) {
  for(var i = 0; i < document.getElementById(e).elements.length; i++) {
    if(document.getElementById(e).elements[i].type == "checkbox")
      document.getElementById(e).elements[i].checked = false;
  }
}