How to make a window of gratitude after sending the form, but not through the alert?

<div id="alert" class="modal">
 <div class="modal-content">
 <span class="close">&times;</span>
 <p>the Form is submitted, we will contact you in 10 minutes..</p>
</div>
</div>

.modal {
 display: none;
 position: fixed;
 z-index: 1;
 padding-top: 100px;
 left: 0;
 top: 0;
 width: 100%;
 height: 100%;
 overflow: auto;
 background-color: rgb(0,0,0);
 background-color: rgba(0,0,0,0.4);
}

.modal-content {
 background-color: #fefefe;
 margin: auto;
 padding: 20px;
 border: 1px solid #888;
 width: 80%;
}

.close {
 color: #aaaaaa;
 float: right;
 font-size: 28px;
 font-weight: bold;
}

.close:hover,
.close:focus {
 color: #000;
 text-decoration: none;
 cursor: pointer;
}

submitHandler: function(form) {
$.ajax({
 type: "POST",
 url: "send.php",
 data: $(form).serialize(),
 success: function (response) {
 (function() {
 const alert = document.querySelector("#alert");
 const close = document.querySelector(".close");

 alert.style.display = "block";

 close.addEventListener("click", function() {
 alert.style.display = "none";
})
})();
$(form)[0].reset();
modal.removeClass('modal--visible');
},
 error: function (response) {
 console.error('request failed' + response);
}
});
}