Validate Alphanumeric Javascript

Validating the input for alphanumeric value only is a very frequent requirement in the applications to ensure special characters are not

In this post, I am sharing a small Javascript Function that ensures that the input can contain alpha or number characters only.

Note: Space or punctuation also are not allowed since those characters are not alpha numeric

On key press the function will validate the character (based on ASCII value) and will not allow you to type if the character is not alphanumeric. If you want to allow any other character then tweak the function accordingly.

<script type="text/javascript">
  function validate(key) {
    var keycode = (key.which) ? key.which : key.keyCode;
    if ((keycode >= 65 && keycode <= 90) || (keycode >= 97 && keycode <= 122) || (keycode >= 48 && keycode <= 57))
      return true;
    else
      return false;
  }
</script>
<asp:TextBox ID="txt1" onkeypress="return validate(event)" runat="server"></asp:TextBox>