Sweetalert2 input validation with AJAX - ajax

Question

I'm using sweetalert2 to set-up multiple inputs as modal (with swal mixin), and I need to verify in server-side if values sent are equal to the ones in database. As example I'm using just a constant value in the .php file. Here's my code:
{
onBeforeOpen: function (dom) {
dom.getElementsByClassName('swal2-input')[0].style = "display: none";
},
html:
"<form action='' method='post'>" +
"<div class='main-cont'>"+
"<span>" +
"Por favor ingresa el codigo de verificacion NUIP "+
"que hemos enviado a tu celular" +
"</span>"+
"<div class='row cuadros'>" +
"<input id='num-1' class='inp-num' data-pos='0' type='text' maxlength='1' name='one' onkeypress='isInputNumber(event)' autofocus='autofocus'/>" +
"<input id='num-2' class='inp-num' data-pos='1' type='text' maxlength='1' name='two' onkeypress='isInputNumber(event)'>" +
"<input id='num-3' class='inp-num' data-pos='2' type='text' maxlength='1' name='three' onkeypress='isInputNumber(event)'>" +
"<input id='num-4' class='inp-num' data-pos='3' type='text' maxlength='1' name='four' onkeypress='isInputNumber(event)'>" +
"</div>" +
"</div>"+
"</form>",
inputValidator: function() {
var nums = Object.values(document.getElementsByClassName("inp-num"));
for(var i = 0; i < nums.length; i++) {
if(!nums[i].value) {
return 'Ingresa el codigo completo';
}
}
$.ajax({
type: "POST",
url: "php/confirma_datos.php",
data: {
"one": $("#num-1").val(),
"two": $("#num-2").val(),
"three": $("#num-3").val(),
"four": $("#num-4").val(),
},
success : function(response) {
if (response == 'true') {
swal('hola');
return 'OK';
} else {
console.log('no coinciden');
}
},
});
},
preConfirm: function () {
return [
$("#num-1").val(),
$("#num-2").val(),
$("#num-3").val(),
$("#num-4").val(),
]
},
},
And in the server side I have.
<?php
$nuip_comp = "1234";
$nuip = $_POST['one'] . "" . $_POST['two'] . "" . $_POST['three']. "" . $_POST['four'] ;
if($nuip_comp == $nuip) {
echo 'true';
} else {
echo 'false';
}
I want to prevent the modal to go to the next step until the values are equal. Any idea on how to do this?
Thanks!