Custom class selectors for WP nav items

wp-nav-classes.php

<?php

	/**
	 * Class selectors added to the menu item's <li> element.
	 */
	function menu_item( $attr, $item ) {

		return $attr;
	}
	add_filter( 'nav_menu_css_class', 'menu_item', 10, 2 );

	/**
	 * Class selectors added to the menu item's <a> element.
	 */
	function menu_link( $attr, $item, $args ) {

		return $attr;
	}
	add_filter( 'nav_menu_link_attributes', 'menu_link', 10, 3 );

	/**
	 * Class selectors added for the menu item's state.
	 */
	function nav_menu_filters( $text ) {
		$replace = array(
			'current_page_item'      => 'is-active',
			'current_page_parent'    => 'is-active',
			'current_page_ancestor'  => 'is-active',
			'current-menu-item'      => 'is-active',
			'menu-item-has-children' => 'has-dropdown',
			'sub-menu'               => 'dropdown',
		);
		$text = str_replace( array_keys( $replace ), $replace, $text );
		return $text;
	}
	add_filter( 'wp_nav_menu', 'nav_menu_filters' );