function addEvent( obj, type, fn ) {
  if ( obj.attachEvent ) {
    obj['e'+type+fn] = fn;
    obj[type+fn] = function(){obj['e'+type+fn]( window.event );}
    obj.attachEvent( 'on'+type, obj[type+fn] );
  } else
    obj.addEventListener( type, fn, false );
}

addEvent(window, "load", isDomReady);

function isDomReady() {
  if(document.getElementById('order_form')){
    var order_form = document.getElementById('order_form');
    var order_inputs = order_form.getElementsByTagName('input');
    var total_price = document.getElementById('total_price');
    var total_post = document.getElementById('total_post');
    for(var x = 0; x < order_inputs.length; x++){
      if(order_inputs[x].className == "order"){
        if(order_inputs[x].id == "item_0") {
          order_inputs[x].checked = true;
        } else {
          order_inputs[x].checked = false;          
        }
        order_inputs[x].onclick = function(){
          var cash = 0;
          for(var z = 0; z < order_inputs.length; z++){
              if(order_inputs[z].className == "order" && order_inputs[z].checked == true){
                cash +=  parseInt(order_inputs[z].value);
              }
          }  
          if(cash > 4000 || cash == 0 ) {   
            total_post.innerHTML = "0,- Kč*";
          } else {
            total_post.innerHTML = "200,- Kč*<br/><small>(168,- Kč bez DPH)</small>";
          }
          cashexvat = Math.ceil(cash/1.19);
          total_price.innerHTML = cash + ",- Kč<br/><small>("+ cashexvat +",- Kč bez DPH)</small>";
        }
      }
    }
  }
  if(document.getElementById('clear_form')){
    document.getElementById('clear_form').onclick = function(){
      var order_form = document.getElementById('order_form');
      var order_inputs = order_form.getElementsByTagName('input');
      document.getElementById('total_price').innerHTML = "0,- Kč";
      for(var x = 0; x < order_inputs.length; x++){
        if(order_inputs[x].className == "order"){
          order_inputs[x].checked = false;
        }      
      }
      return false;
    }
  }
}