function hidden(item){
  var current_item = document.getElementById(item);
  if(current_item.style.display=='none')
    current_item.style.display='';
  else current_item.style.display='none';
}

var hidden_status = true;
function hidden_all(num_item){
  for(i=0; i<num_item; i++){
    var current_item = document.getElementById("cat_" + i);
    if(hidden_status==true)
      current_item.style.display='';
    else current_item.style.display='none';  
  }
  if(hidden_status == true)hidden_status = false;
  else hidden_status = true;
}