FileReader() returning value undefined

Question

How can I return the var validEmails to checkform(). It's undefined right now.

<script type="text/javascript">
function checkfile(form) {

  var reader = new FileReader();

  reader.onload = function(e) {
    var emails = e.target.result;
    var validEmails = parseEmails(emails);
    return validEmails;
  };

  var formFiles = form.files[0];
  reader.readAsText(formFiles);

  function parseEmails(emails) {
    var obj = Papa.parse(emails, { skipEmptyLines: true });

    var valid = 1;
    $.each(obj.data, function(i, v) {
      var email = v[0].trim();
      valid = validEmail(email);
    });

    return valid;
  };

  function validEmail(email) {
    var regex = /^([a-zA-Z0-9_.+-])+\@(([a-zA-Z0-9-])+\.)+([a-zA-Z0-9]{2,4})+$/;
    return regex.test(email);
  };
}

function checkform(form) {
  console.log( checkfile( document.getElementById('recipient_csv') ) );
}
</script>

<form method="post" action="/" enctype="multipart/form-data" onSubmit="return checkform(this);">

  <input id="recipient_csv" type="file" name="recipient_csv" />

</form>

Answer 1

validEmails variable is within the scope of the onload function. Either defined it out the function or remove "var" ( which would make it global variable).

You should check the variables scope of javascript http://www.w3schools.com/js/js_scope.asp