Mostrare/nascondere div tramite select

[bstefano79]

prova così

<script>
function mostraNascondi(selectobj)
{
        if(selectobj.options[selectobj.selectedIndex].value=="alterBook")
        {
                document.getElementById('alter').style.display='block';
        }
        else
        {
                document.getElementById('alter').style.display='none';
        }
}
</script>

<form action="/Libreria_Tweb/Operation" method="post" enctype="multipart/form-data" name="operation" > 


<select name="tipoInfo" onchange="mostraNascondi(this)"> 
<option value="addBook"> Inserisci libro </option> 
<option value="alterBook"> Modifica libro </option>  
</select></p> 
<div id="alter" style="display:none">Vecchio ISBN <input type="text" name="oldIsbn" /></div> 


ISBN: <input type="text" name="isbn" /></p> 


Titolo: <input type="text" name="titolo" /></p> 


Autore: <input type="text" name="autore" /></p> 


Categoria: <select name="categoria"> 
<option value="musica">Musica</option> 
<option value="letteratura">Letteratura</option> 
<option value="cucina">Cucina</option> 
<option value="informatica">Informatica</option> 
</select></p> 


Prezzo: <input type="text" name="prezzo" /></p> 


Copertina: <input type="file" name="copertina"  /></p> 


<input type="submit" name="operation" value="invia"> 
</form>