Proměnná z value inputu

<?php
$b_nick = "Meno";
?>
 
<form name="statistiky" onSubmit="return kontrola();" method="get"><label><b>Nick:</b> </label><input type="text" id="id-inputu" name="nick"><input type="submit"></form>
<span id='nick-test'></span>
 
<script type="text/javascript">
 
var nickName = document.getElementById('id-inputu');
nickName.onkeyup = kontrola;
var b_nick = 'Meno';
var testNicku = document.getElementById('nick-test');
 
function kontrola() {
  if (nickName.value === b_nick) {
    testNicku.innerHTML = 'Nick OK';
    return true;
  }
  else {
    testNicku.innerHTML = 'Spatny nick';
  }
  return false;
}
</script>