before submit

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/limonte-sweetalert2/6.2.0/sweetalert2.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/limonte-sweetalert2/6.2.0/sweetalert2.min.css">

  
  
  <form id="test" action="javascript:alert('success!');">
    <div>
      <input id="deneme" type="text" />
 
      <input type="submit" />
    </div>
  </form>
  <span></span>

CSS

p { margin:0; color:blue; }
  div,p { margin-left:10px; }
  span { color:red; }

JavaScript

$("#test").submit(function() {
  if ($("#deneme").val().length == 3) {
    $("span").text("Validated...").show();
    return true;
  }
  $("span").text("Not valid!").show().fadeOut(1000);
  return false;
});