Validating TR numbers with bootstrap taginputs

validate_taginputs.js

/*
*https://github.com/jackocnr/intl-tel-input
*https://bootstrap-tagsinput.github.io/bootstrap-tagsinput/examples/
*/

$('#send_sms_numbers').on('beforeItemAdd', function(event) {
    // event.item: contains the item
    // event.cancel: set to true to prevent the item getting added
    // TR numbers startswith 90 
    // we also delete 0 at the beginning for our convenience
      if ( event.item.startsWith('90') ) {
          console.log("startswith 90", event.item);
          event.item = event.item.slice(2,); // remove 90
          event.cancel = true; // dont add this
          $('#send_sms_numbers').tagsinput('add', event.item); // add the modified number
          return; // dont evaluate after that
      }
      if ( event.item.startsWith('0') ) {
          console.log("startswith 0", event.item);
          event.item = event.item.slice(1,); // remove 0
          event.cancel = true;
          $('#send_sms_numbers').tagsinput('add', event.item);
          return;
      }
      if (!intlTelInputUtils.isValidNumber(event.item, 'tr') ) { // check if valid number
          event.cancel = true;
          warningAllert('Hatalı veya eksik numara girdiniz.');
      }
  });