Do masking on account number

 

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div id="ccnumber">434343434</div>

<script type="text/javascript">

  $('#ccnumber').text(function(_, val) {

    return val.replace(/\d(?=\d{4})/g, "X");

  });

</script>