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Dynamically populate a Day dropdown menu dependent on the Month selected.

First the Javascript

Place this inbetween the head tags of your document

<script language="javascript">
function focusarea(intMonthID,intNum) {
  this.Num = intNum;
  this.monthID = intMonthID;
}
function getFocusArea() {
  var sSelect = '<select name="dcount">';
  var selectID = document.schedule.mcount.value;
  for (var x=1; x<aFocusArea.length; x++) {
    if (aFocusArea[x].monthID == selectID) {
      for (var i=1; i<aFocusArea[x].Num+1; i++) {
      sSelect = sSelect + '<option>' + [i] + '</option>'
    }
  }
}
sSelect = sSelect + '</select>';
document.all['Focus'].innerHTML = "";
document.all['Focus'].innerHTML = sSelect;
}
var aFocusArea = new Array;
aFocusArea[1] = new focusarea(1,31);
aFocusArea[2] = new focusarea(2,29);
aFocusArea[3] = new focusarea(3,31);
aFocusArea[4] = new focusarea(4,30);
aFocusArea[5] = new focusarea(5,31);
aFocusArea[6] = new focusarea(6,30);
aFocusArea[7] = new focusarea(7,31);
aFocusArea[8] = new focusarea(8,31);
aFocusArea[9] = new focusarea(9,30);
aFocusArea[10] = new focusarea(10,31);
aFocusArea[11] = new focusarea(11,30);
aFocusArea[12] = new focusarea(12,31);
</script>


Just a few notes on the Javascript!


var selectID = document.schedule.mcount.value;
This takes the value from the Month dropdown menu.



  for (var x=1; x<aFocusArea.length; x++) {
    if (aFocusArea[x].monthID == selectID) {
      for (var i=1; i<aFocusArea[x].Num+1; i++) {
      sSelect = sSelect + '<option>' + [i] + '</option>'
    }
  }
}
This part of the function compares the value from the month menu and finds the appropriate array to get the proper day count then populates the day menu with the corresponding number of days.

Place the code below in a place where you can access it, If you are only going to use it on one page then you can put it at the top of your ASP page. If you want multiple pages to access it then what I do is put it in a page called "common.asp" then I use an include at the top of each page I want to use it in IE:
<!-- #include file="common.asp"-->

<%
Sub selectDate
  Response.Write "<select name=""mcount"" OnChange=""getFocusArea();"">" & vbcrlf
  Response.Write "<option value=""0"">Select Month</option>" & vbcrlf
  For mcount = 1 to 12
    Response.Write " <option value="""&mcount&""">" & mcount & "</option>" & vbcrlf
  Next
  Response.Write " </select>" & vbcrlf
%>
<span id="Focus">
    <select name="dcount">
      <option>Select Day</option>
    </select>
</span>
<%
  Response.Write "  <select name=""ycount"">" & vbcrlf
  For ycount = 7 to 20
    If ycount >= 10 Then
      Response.Write " <option>20" & ycount & "</option>" & vbcrlf
    Else
      Response.Write " <option>200" & ycount & "</option>" & vbcrlf
    End If
  Next
  Response.Write " </select>" & vbcrlf
End Sub
%>

To use the Sub Procedure above place the form below where you want the menu to appear on your ASP page:

<form action="myform.asp" name="schedule" method="post">
<% selectDate %>
<input type="submit" value="Submit" />
</form>

Or you can place it inbetween your ASP code:
<%
Response.Write "<form action="myform.asp" name="schedule" method="post" >
Some ASP form code...

selectDate

Some more ASP form Code
</form>
%>
Note that the name of the Form is "schedule" that MUST be included in the form tag.

Try it out!

Well thats all there is to it! I hope you find this article useful!