navigation.js

/**
 * navigation.js
 *
 * Handles toggling the navigation menu for small screens and enables tab
 * support for dropdown menus.
 */
( function() {
    var container, button, menu, links, subMenus;

    container = document.getElementById( 'site-navigation' );
    if ( ! container ) {
        return;
    }

    button = container.getElementsByTagName( 'button' )[0];
    if ( 'undefined' === typeof button ) {
        return;
    }

    menu = container.getElementsByTagName( 'ul' )[0];

    // Hide menu toggle button if menu is empty and return early.
    if ( 'undefined' === typeof menu ) {
        button.style.display = 'none';
        return;
    }

    menu.setAttribute( 'aria-expanded', 'false' );
    if ( -1 === menu.className.indexOf( 'nav-menu' ) ) {
        menu.className += ' nav-menu';
    }

    button.onclick = function() {
        if ( -1 !== container.className.indexOf( 'toggled' ) ) {
            container.className = container.className.replace( ' toggled', '' );
            button.setAttribute( 'aria-expanded', 'false' );
            menu.setAttribute( 'aria-expanded', 'false' );
        } else {
            container.className += ' toggled';
            button.setAttribute( 'aria-expanded', 'true' );
            menu.setAttribute( 'aria-expanded', 'true' );
        }
    };

    // Get all the link elements within the menu.
    links    = menu.getElementsByTagName( 'a' );
    subMenus = menu.getElementsByTagName( 'ul' );

    // Set menu items with submenus to aria-haspopup="true".
    for ( var i = 0, len = subMenus.length; i < len; i++ ) {
        subMenus[i].parentNode.setAttribute( 'aria-haspopup', 'true' );
    }

    // Each time a menu link is focused or blurred, toggle focus.
    for ( i = 0, len = links.length; i < len; i++ ) {
        links[i].addEventListener( 'focus', toggleFocus, true );
        links[i].addEventListener( 'blur', toggleFocus, true );
    }

    /**
     * Sets or removes .focus class on an element.
     */
    function toggleFocus() {
        var self = this;

        // Move up through the ancestors of the current link until we hit .nav-menu.
        while ( -1 === self.className.indexOf( 'nav-menu' ) ) {

            // On li elements toggle the class .focus.
            if ( 'li' === self.tagName.toLowerCase() ) {
                if ( -1 !== self.className.indexOf( 'focus' ) ) {
                    self.className = self.className.replace( ' focus', '' );
                } else {
                    self.className += ' focus';
                }
            }

            self = self.parentElement;
        }
    }
} )();