Q711 How do I tell if a field exists on a form?

<FORM NAME="myform">
<INPUT TYPE="TEXT" NAME="myfield">
</FORM>

<SCRIPT LANGUAGE="JavaScript"><!--
if (document.myform.myfield)
    alert('myfield exists');
else
    alert('myfield does not exist');
if (document.myform.myotherfield)
    alert('myotherfield exists');
else
    alert('myotherfield does not exist');
//--></SCRIPT>