app/assets/javascripts/attendances/attendance_form_events.js
function bindClickToLoadUser() {
$('.user-select').on('change', function(){
const eventId = $('#event_id').val();
const userId = $('.user-select').val();
jQuery.ajax({
url: `/events/${eventId}/attendances/user_info.js`,
type: "GET",
data: `&user_id=${userId}`
});
});
}