how to add data attribute to a <li> element in wordpress nav menu

I'm using fullpage.js on a wordpress site and would like to use one of it's function wicht is to add a class on a li. But to do this you need to add the data attribute data-menuanchor .

I have seen this:

add_filter( 'nav_menu_link_attributes', 'my_nav_menu_attribs', 10, 3 );
function my_nav_menu_attribs( $atts, $item, $args )
{
  // The ID of the target menu item
  $menu_target = 113;

  // inspect $item
  if ($item->ID == $menu_target) {
    $atts['data-menuanchor'] = 's1';

  }
  return $atts;
}

It works excepts that it adds the attribute to the a tag and need it to be on the li tag.

Also, if I want to do it to all the items on the menu. Do I need to do this function for all the items? And I suppose I have to rename the function each time?

Thanks

I'm not sure WP has a specific filter/method for this. You're gonna have to do some manual DOM manipulation along with wp_nav_menu_items.

https://developer.wordpress.org/reference/hooks/wp_nav_menu_items/

function addDataAttr( $items, $args ) {
    $dom = new DOMDocument();
    $dom->loadHTML($items);
    $find = $dom->getElementsByTagName('li');

    foreach ($find as $item ) :
        $item->setAttribute('data-menuanchor','s1');
    endforeach;

    return $dom->saveHTML();

}

add_filter('wp_nav_menu_items', 'addDataAttr', 10, 2);