Example of intl-tel-input initialization on wordpress custom plugin and handling on wc-ajax=checkout_update_order_review

sample-intl-tel-input.php

function init_tel(){
$utils_url = plugins_url('/js/utils.js', __FILE__);
?>
<script>
  var input = document.querySelector("#phone");
  var iti = window.intlTelInput(input,{
    utilsScript: "<?php echo $utils_url; ?>",
  	// the countries at the top of the list. defaults to united states and united kingdom
    preferredCountries: [ "my", "us", "gb" ],
    autoPlaceholder: null,
    separateDialCode: true,
    hiddenInput: "mobileNo"
   });
   var hiddenInput = document.querySelector('#mobileNo');
   hiddenInput.value = "<?php echo $POST["mobileNo"];?>";
</script>
<?php
}