Validation

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.4.1/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.11.2/css/all.min.css">
<link rel="stylesheet" href="style.css">
<title>Title</title>
</head>
<body>
    <div class="container-fluid" id="container-wrapper">
        <div class="d-sm-flex align-items-center justify-content-between mb-4">
          <h1 class="h3 mb-0 text-gray-800">Data Pemilik</h1>
          <ol class="breadcrumb">
            <li class="breadcrumb-item"><a href="./">Home</a></li>
            <li class="breadcrumb-item">Tables</li>
            <li class="breadcrumb-item active" aria-current="page">Data Pemilik</li>
          </ol>
        </div>

        <!-- Row -->
        <div class="card mb-4">
          <div class="card-header py-3 d-flex flex-row align-items-center justify-content-between">
            <h6 class="m-0 font-weight-bold text-primary">Input Data Pemilik</h6>
          </div>
          <div class="card-body">
            <form method="post" action="#" enctype="multipart/form-data" class="formInputPemilik">
             <div class="form-group">
              <label for="nik">NIK</label>
              <input type="number" class="form-control" name="nik"  placeholder="Masukan ID pemilik" required="">

              <small class="text-danger d-none validation-nik">Tidak boleh lebih atau kurang dari 16 digit</small>


            </div>
            <div class="form-group">
              <label for="nm_pemilik">Nama</label>
              <input type="type" class="form-control" name="nm_pemilik"placeholder="Masukan Pemilik" required="">
            </div>
             <div class="form-group">
              <label for="no_telp">No Telp</label>
              <input type="number" class="form-control" name="no_telp"placeholder="Masukan No Telp..." required="">
            </div>
            <div class="form-group">
              <label for="no_telp">Alamat</label>
              <textarea name="alamat" rows="5" class="form-control" placeholder="Masukan Alamat..." required=""></textarea>
            </div>
            <div class="form-group">
              <label for="username">Username</label>
              <input type="username" class="form-control" name="username"placeholder="Masukan Username..">
            </div>
            <div class="form-group">
              <label for="password">Password</label>
              <input type="password" class="form-control" name="password"placeholder="Masukan Username..">
            </div>
      <div class="form-group">
       <button class="btn btn-success" type="submit">Simpan</button>
      </form>
      </div>
      </div>
      </div>
      <!--Row-->

      </div>
      </div>
      </div>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.4.1/js/bootstrap.min.js"></script>

    <!-- validation -->
    <script>
        $(".formInputPemilik").submit(function(e){
            e.preventDefault();
            var nik = $("[name='nik']").val();
            if(nik.length == 16){
                $.ajax({

                });
            }else{
                $(".validation-nik").addClass("d-block").removeClass("d-none");
            }
        });
    </script>
</body>
</html>