add_action without modifying crud

I have a table where I have the lines:

$crud->add_action('Snapshot', '', 'Configure/snapshot', 'Select');

$output = $crud->render();

My function called snapshot:

public function snapshot($post_array, $primary_key)

{
echo '<script> window.postMessage({ type: "FROM_PAGE_TO_CONTENT_SCRIPT",text: "Hello from the webpage!" }, "*");</script>';
}

Snapshot uses javascript to write a message out to a content script. I thought that after snapshot() runs, I would not even redraw the crud. But the crud blanks out the page. Any idea how I can get snapshot to run without affecting the UI?

add_action without modifying crud

richb201