Replace small-menu.js with navigation.js inspired by Twenty Twelve.

Doesn't use jQuery, slightly easier to understand, uses a media query for max-width, rather than JS events making it faster to respond.

functions.php

@@ -102,7 +102,7 @@ add_action( 'widgets_init', '_s_widgets_init' );
 function _s_scripts() {
 	wp_enqueue_style( 'style', get_stylesheet_uri() );
 
-	wp_enqueue_script( 'small-menu', get_template_directory_uri() . '/js/small-menu.js', array( 'jquery' ), '20120206', true );
+	wp_enqueue_script( 'navigation', get_template_directory_uri() . '/js/navigation.js', null, '20120206', true );
 
 	if ( is_singular() && comments_open() && get_option( 'thread_comments' ) ) {
 		wp_enqueue_script( 'comment-reply' );

header.php

@@ -51,8 +51,8 @@
 			<h2 class="site-description"><?php bloginfo( 'description' ); ?></h2>
 		</hgroup>
 
-		<nav role="navigation" class="site-navigation main-navigation">
-			<h1 class="assistive-text"><?php _e( 'Menu', '_s' ); ?></h1>
+		<nav role="navigation" class="site-navigation main-navigation" id="site-navigation">
+			<h1 class="menu-toggle"><?php _e( 'Menu', '_s' ); ?></h1>
 			<div class="assistive-text skip-link"><a href="#content" title="<?php esc_attr_e( 'Skip to content', '_s' ); ?>"><?php _e( 'Skip to content', '_s' ); ?></a></div>
 
 			<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>

js/navigation.js

@@ -0,0 +1,32 @@
+/**
+ * navigation.js
+ *
+ * Handles toggling the navigation menu for small screens.
+ */
+( function() {
+	var button    = document.getElementById( 'site-navigation' ).getElementsByTagName( 'h1' )[0],
+	    menu      = document.getElementById( 'site-navigation' ).getElementsByTagName( 'ul' )[0];
+	    container = document.getElementById( 'site-navigation' );
+
+	if ( undefined == button || undefined == menu )
+		return false;
+
+	button.onclick = function() {
+		if ( -1 == menu.className.indexOf( 'nav-menu' ) )
+			menu.className = 'nav-menu';
+
+		if ( -1 != button.className.indexOf( 'toggled-on' ) ) {
+			button.className = button.className.replace( ' toggled-on', '' );
+			menu.className = menu.className.replace( ' toggled-on', '' );
+			container.className = container.className.replace( ' main-small-navigation', ' main-navigation' );
+		} else {
+			button.className += ' toggled-on';
+			menu.className += ' toggled-on';
+			container.className = container.className.replace( ' main-navigation', ' main-small-navigation' );
+		}
+	};
+
+	// Hide menu toggle button if menu is empty.
+	if ( ! menu.childNodes.length )
+		button.style.display = 'none';
+} )();

js/small-menu.js

@@ -1,39 +0,0 @@
-/**
- * Handles toggling the main navigation menu for small screens.
- */
-jQuery( document ).ready( function( $ ) {
-	var $masthead = $( '#masthead' ),
-	    timeout = false;
-
-	$.fn.smallMenu = function() {
-		$masthead.find( '.site-navigation' ).removeClass( 'main-navigation' ).addClass( 'main-small-navigation' );
-		$masthead.find( '.site-navigation h1' ).removeClass( 'assistive-text' ).addClass( 'menu-toggle' );
-
-		$( '.menu-toggle' ).unbind( 'click' ).click( function() {
-			$masthead.find( '.menu' ).toggle();
-			$( this ).toggleClass( 'toggled-on' );
-		} );
-	};
-
-	// Check viewport width on first load.
-	if ( $( window ).width() < 600 )
-		$.fn.smallMenu();
-
-	// Check viewport width when user resizes the browser window.
-	$( window ).resize( function() {
-		var browserWidth = $( window ).width();
-
-		if ( false !== timeout )
-			clearTimeout( timeout );
-
-		timeout = setTimeout( function() {
-			if ( browserWidth < 600 ) {
-				$.fn.smallMenu();
-			} else {
-				$masthead.find( '.site-navigation' ).removeClass( 'main-small-navigation' ).addClass( 'main-navigation' );
-				$masthead.find( '.site-navigation h1' ).removeClass( 'menu-toggle' ).addClass( 'assistive-text' );
-				$masthead.find( '.menu' ).removeAttr( 'style' );
-			}
-		}, 200 );
-	} );
-} );

style.css

@@ -405,12 +405,24 @@ a:active {
 
 /* Small menu */
 .menu-toggle {
+	display: none;
 	cursor: pointer;
 }
-.main-small-navigation .menu {
+
+.main-small-navigation ul {
 	display: none;
 }
 
+@media screen and (max-width: 600px) {
+	.menu-toggle,
+	.main-small-navigation ul.nav-menu.toggled-on {
+		display: block;
+	}
+
+	.main-navigation ul {
+		display: none;
+	}
+}
 
 /* =Content
 ----------------------------------------------- */