Il calcolo viene eseguito in tempo reale, al totale vengono aggiunti 2 decimali.codice:<head> <script type="text/javascript"> function bill(){ var se=Number(document.getElementById('se').value); var notti=Number(document.getElementById('notti').value); var degustazioni=Number(document.getElementById('degustazioni').value); var total=(se*notti)+degustazioni; document.getElementById('bill').innerHTML='Totale: € '+total.toFixed(2); } window.onload=bill; </script> </head> <body> <select name="se" id="se" onchange="bill()"> <option value="25" selected="selected">Prima colazione</option> <option value="35">Mezza pensione</option> <option value="40">Pensione completa</option> </select> <select name="notti" id="notti" onchange="bill()"> <option value="1" selected="selected">1</option> <option value="2">2</option> <option value="3">3</option> <option value="4">4</option> <option value="5">5</option> <option value="6">6</option> <option value="7">7</option> </select> <select name="degustazioni" id="degustazioni" onchange="bill()"> <option value="10" selected="selected">2</option> <option value="15">3</option> <option value="20">4</option> <option value="25">5</option> <option value="30">6</option> <option value="35">7</option> <option value="40">8</option> <option value="45">9</option> <option value="50">10</option> </select> <div id="bill"></div> </body>