function switch1(div,divids) {
//var option=['cover','backcover','jj'];
var option = divids;

for(var i=0; i<option.length; i++) {
  if (document.getElementById(option[i])) {
  obj=document.getElementById(option[i]);
  obj.style.display=(option[i]==div)? "block" : "none";
}
}
}