+ * @since 4.7.0 Added the `item_spacing` argument.
+ *
+ * @staticvar array $menu_id_slugs
+ *
+ * @param array $args {
+ * Optional. Array of nav menu arguments.
+ *
+ * @type int|string|WP_Term $menu Desired menu. Accepts (matching in order) id, slug, name, menu object. Default empty.
+ * @type string $menu_class CSS class to use for the ul element which forms the menu. Default 'menu'.
+ * @type string $menu_id The ID that is applied to the ul element which forms the menu.
+ * Default is the menu slug, incremented.
+ * @type string $container Whether to wrap the ul, and what to wrap it with. Default 'div'.
+ * @type string $container_class Class that is applied to the container. Default 'menu-{menu slug}-container'.
+ * @type string $container_id The ID that is applied to the container. Default empty.
+ * @type callable|bool $fallback_cb If the menu doesn't exists, a callback function will fire.
+ * Default is 'wp_page_menu'. Set to false for no fallback.
+ * @type string $before Text before the link markup. Default empty.
+ * @type string $after Text after the link markup. Default empty.
+ * @type string $link_before Text before the link text. Default empty.
+ * @type string $link_after Text after the link text. Default empty.
+ * @type bool $echo Whether to echo the menu or return it. Default true.
+ * @type int $depth How many levels of the hierarchy are to be included. 0 means all. Default 0.
+ * @type object $walker Instance of a custom walker class. Default empty.
+ * @type string $theme_location Theme location to be used. Must be registered with register_nav_menu()
+ * in order to be selectable by the user.
+ * @type string $items_wrap How the list items should be wrapped. Default is a ul with an id and class.
+ * Uses printf() format with numbered placeholders.
+ * @type string $item_spacing Whether to preserve whitespace within the menu's HTML. Accepts 'preserve' or 'discard'. Default 'preserve'.
+ * }
+ * @return object|false|void Menu output if $echo is false, false if there are no items or no menu was found.