JavaScript validation before AJAX submission

Question

I'm trying to validate a form before allowing my ajax submission,however I have two problems. The first problem being I don't know how to best go about validating before submission (most professional process). The second problem being, what is preventing my validation code I currently from working? Looking to become more efficient so all input is welcome. Thanks a ton.

 $('#form-reg').on('submit', function(){

     var bool = false;
     var name = document.getElementById('#name-reg');
     var email = document.getElementById('#email-reg');

     console.log(name);
     console.log(email);
     if(!/[^a-zA-Z]/.test(name)){
       bool = true;
     }
     else{
       bool = false;
     }
     if(bool == true){
        console.log(document.getElementById('#name-reg'));
        $('#form-reg').slideUp('slow');
        // serialize the form
        var formData = $(this).serialize();
        console.log(formData);
        $.ajax({
            type        : 'POST',
            url         : 'register.php',
            data        : formData,

            success: function() {
              alert("Success");
            },
             error: function(xhr) {
              alert("fail");
            }
        })
        .done(function (data) {
              document.getElementById('form-reg').reset();

        })
        .fail(function (error) {
            alert("POST failed");
        });
        //return false;
      }
      else {
        alert('try again');
      }
  });

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js" type="text/javascript">

  <form id = "form-reg">
      <label id ="x" for="name">Name</label>
      <input id="name-reg" name="name"></br>
      <label id = "y" for="email">Email</label>
      <input id="email-reg" name="email"></br>
      <input type="submit" value="submit" id = "submit-reg">
    </form>

Answer 1

The issue with your code is you have to stop the form submit like:

$('#form-reg').on('submit', function(e){
  e.preventDefault();

and after checking the validation, submit the form if validation succeeds.

Answer 2

Although it is a minor answer, I will post it anyway. The problem looks like the use of

var name = document.getElementById('#name-reg');

the # is causing the first problem and should be

var name = $('#name-reg').val();

$('#form-reg').on('submit', function(){

     var bool = false;
     var name = $('#name-reg').val();
     var email = $('#email-reg').val();

     console.log(name);
     console.log(email);
     if(!/[^a-zA-Z]/.test(name)){
       bool = true;
     }
     else{
       bool = false;
     }
     if(bool == true){
        console.log($('#name-reg').val());
        $('#form-reg').slideUp('slow');
        // serialize the form
        var formData = $(this).serialize();
        console.log(formData);
        $.ajax({
            type        : 'POST',
            url         : 'register.php',
            data        : formData,

            success: function() {
              alert("Success");
            },
             error: function(xhr) {
              alert("fail");
            }
        })
        .done(function (data) {
              document.getElementById('form-reg').reset();

        })
        .fail(function (error) {
            alert("POST failed");
        });
        //return false;
      }
      else {
        alert('try again');
      }
  });

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js" type="text/javascript">

  <form id = "form-reg">
      <label id ="x" for="name">Name</label>
      <input id="name-reg" name="name"></br>
      <label id = "y" for="email">Email</label>
      <input id="email-reg" name="email"></br>
      <input type="submit" value="submit" id = "submit-reg">
    </form>