The delete button does not work correctly

I want that when you press delete incident, an alert will appear to make sure that it is deleted or not, the problem is that whenever I press cancel, the incident is deleted. Can somebody help me?

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
// Si se ha pulsado el boton de eliminar incidencia
if (isset($_POST["eliminarInci"])) {
  // Capturamos el valor de $codTarea del campo oculto del formulario
  $codTarea = $_POST["codigoTarea"];
  // Borramos la tarea seleccionada
  require_once('funciones/conexion.php');
  try {
    $deleteIncidencia = "DELETE FROM tareas WHERE COD_TAREA = ?";
    $preparada = $db->prepare($deleteIncidencia);
    $preparada->execute(array($codTarea));
    // Cuando la consulta se ejecute se elimina
    if ($preparada) {
      print "
        <script>
          var result = window.confirm('¿Seguro que quieres borrar esta incidencia?');
          if(result){
            window.location = 'admin.php';
          }
          else{
            window.location = 'admin.php';
          }
        </script>";
        exit;
    }
  } catch (Exception $e) {
    echo "Error: " . $e->getMessage();
  }
}
}
?>