Dynamic Checkbox to clear Textbox

[mschubert]

I am pretty new to javascript so bear with me. I am populating a dynamic textbox on pageload and creating a dynamic checkbox also on page load. I want to check the checkbox and have 2 textboxes clear. I am getting the error 'null' is null or not an object. Here is my code:

<script type="text/javascript" language="javascript">
  function CustNameClear()
  {
   var FName = document.getElementById('tbFName');
   var LName = document.getElementById('tbLName');
   FName.value = '';
   LName.value = '';
  }
  </script>
Dim cbNewUser As New CheckBox
Dim tbFName As New TextBox()
Dim tbLName As New TextBox()
 Dim DBGetCustCmd As SqlCommand = New SqlCommand("usp_Get_Barcode_Customer", DBConn)
  DBGetCustCmd.CommandType = CommandType.StoredProcedure
  DBGetCustCmd.Parameters.AddWithValue("@barcode", barcode)
If Not Page.IsPostBack Then
   Dim reader As SqlDataReader = DBGetCustCmd.ExecuteReader()
   Try
    While reader.Read()
     tbFName.Text = reader.Item("FName")
     tbLName.Text = reader.Item("LName")
     tbAddr1.Text = reader.Item("Addr1")
     tbAddr2.Text = reader.Item("addr2")
     tbCity.Text = reader.Item("city")
     strState = reader.Item("state")
     tbZip.Text = reader.Item("Zip")
     If Not reader.Item("Zip4").ToString = Nothing Then
      tbZip4.Text = reader.Item("Zip4")
     End If
     lbCouponType.Text = reader.Item("Description")
     If Not reader.Item("Email").ToString = Nothing Then
      tbEmail.Text = reader.Item("Email")
     End If
     If Not reader.Item("Phone").ToString = Nothing Then
      tbPhone.Text = reader.Item("Phone")
     End If
    End While
   Finally
    reader.Close()
   End Try
  End If
plNewUser.Controls.Add(cbNewUser)
  cbNewUser.ID = "cbNewUser"
plFName.Controls.Add(tbFName)
plLName.Controls.Add(tbLName)
cbNewUser.Attributes.Add("onClick", "CustNameClear()")

[rocknbil]

Welcome aboard mschubert, my .asp/vbscript is a bit rusty but I have an idea what the problems is:

<script type="text/javascript" language="javascript">
function CustNameClear()
{
var FName = document.getElementById('tbFName');
var LName = document.getElementById('tbLName');
FName.value = '';
LName.value = '';
}
</script>
..........
Dim tbFName As New TextBox()
Dim tbLName As New TextBox()
....
tbFName.Text = reader.Item("FName")
tbLName.Text = reader.Item("LName")

Tell me, is New Textbox() an internal command that creates the text field or is is a function you wrote yourself? Does it create input type="text" or a textarea? (either should work, presuming text input.) If it's internal, review the documentation; if you wrote it yourself, easy enough - the text box is most likely missing an id attribute:

<input type="text" name="tbFName" id="tbFName">

or

<textarea name="tbFName" id="tbFName"></textarea>

Looking at your ASP, it might be as simple as

tbFName.Attributes.Add("id", "tbFName")
tbLName.Attributes.Add("id", "tbLName")

It's perfectly legitimate to have the name and ID the same value; the exception is form array objects, such as radio buttons, where all items in the array have the same name but you must add a different ID for each member. ID's must be unique in the context of the document.

If it's already generating an ID field, then it's something else, possibly invalid HTML breaking the Javascript. An aside, and unrelated, it's always best to test for document.GetElementById first, avoiding sporadic errors:

<script type="text/javascript"> 
 function CustNameClear() { 
 if (document.getElementById) { 
  document.getElementById('tbFName').value=''; 
  document.getElementById('tbLName').value=''; 
 } 
 } 
</script>