Question

I wrote this function to tell the user that the field that they forget to fill out is required, it works but for only a second and then it disappears?

function proc(){
   var errmsg = "";
        if (document.forms["newUser"]["fName"].value == "")
        {
                errmsg += "*This field is required";
                document.getElementById('first_name_error').innerHTML = errmsg;
        }

Why is it only writting to the form page for a less than a second?

Answer 1

The form is probably submitting and reloading. If you are running validation from a submit handler, have the function return false to stop submit:

<form ... onsubmit="return validateForm(this);" ...>


function validateForm(form) {

  var isValid = true;

  // do validation - set isValid to false if any test fails

  return isValid;
}