Add a body class when there are items in the Woocommerce cart

woocommerce-body-class-cart-items.php

<?php

// Add a body class via the body_class filter in WP
// =============================================================================
add_filter( 'body_class', 'mb_body_class_for_cart_items' );
function mb_body_class_for_cart_items( $classes ) {
    if( ! WC()->cart->is_empty() ){
        $classes[] = 'cart-has-items';
    }
    return $classes;
}

// Add a body class via javascript for AJAX enabled sites
// =============================================================================
add_action( 'wp_footer', 'mb_body_class_for_ajax_add_to_cart' );
function mb_body_class_for_ajax_add_to_cart() {
?>
  <script type="text/javascript">
    (function($){
      $('body').on( 'added_to_cart', function(){
        if( ! $(this).hasClass('cart-has-items') ){
          $(this).addClass('cart-has-items');
        }
      });
    })(jQuery);
  </script>
<?php
}

@andrewjohnstrong not sure, why you would need that inside your class, but this function has the cart count: WC()->cart->get_cart_contents_count()