<input type="email" class="form__field" placeholder="Username or email" name="login_form[username]" id="login_form[username]" value="email" required />
<input type="email" class="form__field" placeholder="Username or email" name="login_form[password]" id="login_form[username]" value="email" required />
  
  let $data = new FormData($(this).get(0));
$.ajax({
                url: "form.php",
                type: "POST",
                data: $data,
                dataType: "JSON",
                processData: false,
                contentType: false,
                cache: false,
                async: true
            });