JavaScript to verify that form input is all letters or all numbers


The form below has two fields containing a date. Click the "Calculate Difference" link to calculate the difference in minutes.

Start Time=
End Time=
Calculate Difference
Difference in Minutes=

<form id="pirep" runat="server">

  Start Time= <input id="st" name="st" value="01:10:00 08-08-2007" />

  <br />End Time= <input id="lt" name="lt" value="02:00:00 08-08-2007" />

  <br /><a href="javascript:setvars();">Calculate Difference</a>

  <br />Difference in Minutes= <input id="th" name="th" value="" />

</form>

<script>

function setvars()

{

var minutes = 1000 * 60;

var hours = minutes * 60;

var d1 = document.pirep.st.value;

var d2 = document.pirep.lt.value;

var e = Date.parse(d1);

var e1 = Date.parse(d2);

var y = e/minutes;

var y1 = e1/minutes;

var final = y1-y;

//document.pirep.st.value = e;

//document.pirep.lt.value = e1;

document.pirep.th.value = final;

}

</script>