Add a data attribute of page/post to a WordPress Menu ( wp_nav_menu() )

functions.php

/**
 * Add a data attribute of page/post to a WordPress Menu

 * Add this to your functions.php file
 *
 * This function will add the page/post ID of item the menu links to 
 * when using wp_nav_menu(); to build the menu.
 *
 *  Example:
 *
 *  <li id="menu-item-28" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-28">
 *     <a href="http://mysite.dev/my-page/" data-id="9">My Page</a>
 *  </li>
 *
 *  @link https://developer.wordpress.org/reference/functions/wp_nav_menu/
 *  @link https://developer.wordpress.org/reference/functions/get_post_meta/
 */


add_filter( 'nav_menu_link_attributes', 'tmg__menu_atts', 10, 3 );

function tmg__menu_atts( $atts, $item, $args )
{
    $atts['data-id'] = get_post_meta( $item->ID, '_menu_item_object_id', true );
  	return $atts;
}

This was the perfect filter to use with the Root Inc site, converting their navigation data attributes, including anchor class to be used in the WordPress wp_nav_menu() function. It will save time in changing the configuration of using the hard coded data attributes. I do not need this to get the ID but will use it to manipulate other keys for the post meta of the link.