Show alert box in admin panel when click on the Database backup button

<li class="" <?php if(strpos($m[$i]->menu_url,'db_backup')) echo 'id="db_download"'?>><a href="<?=base_url()?><?=$m[$i]->menu_url?>"><span class="menu_icon"><i class="material-icons">&#xE871;</i></span> <span class="menu_title">
  <?=$m[$i]->menu_name?>
  </span> </a> </li>

<script>
document.getElementById("db_download").addEventListener("click", function(event){
var r = confirm("Are you sure to back up database");
if (r == true) {
   return true;
} else {
   event.preventDefault();
}
    return true;
});
</script>