modify wordpress menu for anchor links in semi-single page site

gistfile1.txt

/**
 * modify primary menu so that the anchor links always point back to the homepage
 */
if( ! function_exists('nav_items') ) {
	add_filter( 'wp_get_nav_menu_items','nav_items', 11, 3 );

	function nav_items( $items, $menu, $args ) 
	{
	    if( is_admin() )
	        return $items;

	    // check whether it's the homepage -- if anchor links are all on the homepage anyway, no need to modify
	    // also check whether it's our theme location -- change "primary" to your theme location
	    if ( ! is_home() && $menu->slug === 'primary')

		    foreach( $items as $item ) 
		    {
			// get the end of the URL for use
	        	$hash = $item->url;
			if ( substr( $hash, 0, 1 ) === "#" )
	        		// append the hash URL to the site URL (homepage where anchor links are)
	        		$item->url = site_url() . $hash;
		    }
		    return $items;
	}
}