Due decimali
codice:
function Decimali(num,num2){
//converto in numeri
var somma = parseFloat(num)+parseFloat(num2);
//imposto i decimali
var format = (Math.round(somma*100)/100);
document.getElementById('tot').value=format;
}
<input type="text" id="importo1" name="importo1" value="1.22" />
<input type="text" id="importo2" name="importo2" value="1" />
<input type="button" id="calcola" name="calcola" value="calcola" onclick="Decimali(document.getElementById('importo1').value,document.getElementById('importo2').value);" />
<input type="text" id="tot" name="tot" />