How to add category post count in main navigation menu [closed]

This can be achieved many ways. But, the below method is most prominent to me.

add_filter('the_title', 'wpse165333_the_title', 10, 2);
function wpse165333_the_title($title, $post_ID)
{
    if( 'nav_menu_item' == get_post_type($post_ID) )
    {
        if( 'taxonomy' == get_post_meta($post_ID, '_menu_item_type', true) && 'category' == get_post_meta($post_ID, '_menu_item_object', true) )
        {
            $category = get_category( get_post_meta($post_ID, '_menu_item_object_id', true) );
            $title .= sprintf(' (%d)', $category->count);
        }
    }
    return $title;
}

Note: $category->count doesn’t always contain the proper value of
posts. In case any other CPT is using category as taxonomy, the
count would be combination of posts and CPTs.

Usage: The code should go on your child theme’s functions.php file
(if exists), or the parent theme’s functions.php file or either in a
plugin.