"a_location=abc&a_headline=def"

(function ($) {

    "use strict";

    function process_new_post(postData) {

        $.ajax({

            url:"createpost.php",

            method:"POST",

            data:  postData ,

            contentType: false,

            processData: false,

            cache: false,

            success:function(response)

            {

                alert(response);

            },

            error:function(jqXHR, textStatus, errorThrown){

                console.error("AJAX Request Error:", textStatus, errorThrown);

            }

        });

    }

    $(document).ready(function () {

        var forms = document.querySelectorAll('.needs-validation');

        Array.prototype.slice.call(forms)

            .forEach(function (form) {

                form.addEventListener('submit', function (event) {

                    Array.from(form.elements).forEach((input) => {

                       if ( (input.value.trim()==='') && (input.type!=='button') && (input.type!=='submit') ) {

                         input.value = '';

                       }

                    });

                    if ( !form.checkValidity() ) {

                      event.preventDefault();

                      event.stopPropagation();

                    }

                    else {

                        event.preventDefault();

                        process_new_post( $("#formcreatenewpost").serialize() );

                    }

                    form.classList.add('was-validated')

              }, false);

        });

    });

})(jQuery);

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

<form class="needs-validation" id="formcreatenewpost" method="post" enctype="multipart/form-data" novalidate>

    <div class="row g-3">

        <div class="col-md-6">

            <div class="form-floating">

                <input type="text" class="form-control" name="a_location" id="a_location" placeholder="Town(s)" required>

                <label for="a_location">Town(s)</label>

            </div>

        </div>

        <div class="col-12">

            <div class="form-floating">

                <input type="text" class="form-control" name="a_headline" id="a_headline" placeholder="Headline" required>

                <label for="a_headline">Headline</label>

            </div>

        </div>

        <div class="col-4 gy-5">                                    

            <button class="btn btn-primary w-100 py-3" type="submit" id="postcreatenewpost">Post</button>

        </div>

    </div>

</form>