Question

I would like to perform form validation using JavaScript to check for input field only to contain numeric characters.So far, the validation checks for the field not being empty – which works fine.However, numeric characters validation is not working.I would be grateful for any help.Many thanks.

<script type="text/javascript">
//form validation
function validateForm()
{
var x=document.forms["cdp_form"]["univer_number"].value
if (x==null || x=="")
  {
  alert("University number (URN) field must be filled in");
  cdp_form.univer_number.focus();
  return false;
  }
else if (is_valid = /^[0-9]+$/.test(x))
    {
    alert("University number (URN) field must have numeric characters");
    cdp_form.univer_number.focus();
    return false;
  }
}
</script>


<input type ="text" id="univer_number" maxlength="7"    size="25"   name="univer_number" />

Answer 1

You need to test for the negation of the RegExp because you want the validation to alert upon failure, so just add ! in front of it:

else if (is_valid = !/^[0-9]+$/.test(x))

See example →