function AddBook(id)
{
	nllibres[id]++;
	document.getElementById('uni'+id).innerHTML=nllibres[id];
	RecalculaTotal();
}

function DelBook(id)
{
	if(nllibres[id]>0) nllibres[id]--;
	document.getElementById('uni'+id).innerHTML=nllibres[id];
	RecalculaTotal();
}


function RecalculaTotal()
{
	// calculem preu llibres
	apreu = 0;
	cadena="";
	for(i=0;i<preus.length;i++)
	{
		apreu += nllibres[i]*preus[i];
		cadena += nllibres[i]+',';
	}
	// recollim transport si preu superior a 99
	if(apreu>0)
	{
	
		ptrans=document.getElementById('ttrans').options[document.getElementById('ttrans').selectedIndex].value;
		
		if(ptrans==0 && apreu>=90)
		{
			document.getElementById('ptransport').innerHTML=texte_gratis;
		}
		else
		{
			if(apreu<90 && ptrans!=0)
			{
				preu = transport[ptrans]+10;
				document.getElementById('ptransport').innerHTML=(preu.toFixed(2));
			}
			else
			{
				document.getElementById('ptransport').innerHTML=(transport[ptrans].toFixed(2));
				preu=transport[ptrans];
			}
			apreu+=preu;
		}
	
	}
	else
	{
		document.getElementById('ptransport').innerHTML='';
	}
		
	
	// valor total
	document.getElementById('ptotal').innerHTML=apreu.toFixed(2);
	document.getElementById('preutotal').value=apreu.toFixed(2);
	document.getElementById('select_llibres').value=cadena;
	
}

function ObraRegal()
{
	if(document.getElementById('siregal').checked) document.getElementById('input_regal').style.visibility='visible';
	else document.getElementById('input_regal').style.visibility='hidden';
}