Check if character is numeric

[PedroDePacos]

I've written a client-side validation function (for a textbox) that checks if the key pressed by the user is numeric. I cannot get it to work properly, however. The following code does not prevent the user from entering a non-numeric character, but it does prevent the user from entering two non-numeric characters. For example if the user enters a "1" and the a "d", the textbox will display "1d". The next time the user presses a key, the "d" is removed and whatever character the user pressed replaces the "d". I don't want the textbox to display the character unless it is numeric.


'The following is entered in the codebehind

 
Dim txtQuantity As TextBox = e.Item.Cells(4).FindControl("txtQuantity") 
txtQuantity.Attributes.Add("onkeypress", "IsNumeric(" & txtQuantity.ClientID & ",'Integer')")

'this is the javascript function called when the textbox's onkeypress event is fired

 
function IsNumeric(TextBox,strType) 
//  check for valid numeric strings      
{ 
if (strType="Decimal") 
  { 
  var strValidChars = "0123456789."; 
  } 
else if (strType="Integer") 
  { 
  var strValidChars = "0123456789"; 
  } 
var strString; 
var strChar; 
strString=TextBox.value; 

for (i = 0; i < strString.length; i++) 
  { 
  strChar = strString.charAt(i); 
  if (strValidChars.indexOf(strChar) == -1) 
      { 
      TextBox.value = TextBox.value.substring(0, i); 
     TextBox.value.length = i 
      event.returnValue = false; 
      } 
  } 
}

I'm not very proficient in Javascript so I'd appreciate any suggestions.

[PedroDePacos]

Resolved