Combine Primary and Secondary Menu into one Responsive Menu

responsive-menu.js

/* Make sure your Menus are named Primary Navigation and Secondary Navigation in Appearance > Menus */

(function( window, $, undefined ) {
	'use strict';
 
	$('.nav-primary').before('<button class="menu-toggle" role="button" aria-pressed="false"></button>'); // Add toggles to menus
	$('nav .sub-menu').before('<button class="sub-menu-toggle" role="button" aria-pressed="false"></button>'); // Add toggles to sub menus
 
	// Show/hide the navigation
	$('.menu-toggle, .sub-menu-toggle').click(function() {

		if ($(this).attr('aria-pressed') == 'false' ) {
			$(this).attr('aria-pressed', 'true' );
		}
		
		else {
			$(this).attr('aria-pressed', 'false' );
		}

		$(this).toggleClass('activated');
		$(this).next('nav, .sub-menu').slideToggle('fast', function() {

			return false;
			// Animation complete.
		 });
		 
	});

	var isMobile = window.innerWidth <= 768; // set the variable
	isMobile = !isMobile; // force the first resize
    
	$(window).resize(function() {
        
		if(window.innerWidth > 768 && isMobile) {
			isMobile = false; // this IS NOT a mobile size
			$("#menu-secondary-navigation").appendTo(".nav-secondary .wrap");
			$("nav.nav-secondary").show();
		}

		else if(window.innerWidth <= 768 && !isMobile) {
			isMobile = true; // this IS a mobile size
			$("#menu-secondary-navigation").insertAfter("#menu-primary-navigation");
			$("nav.nav-secondary").hide();
		}

	});

	// check the size when its adjusted...
		$(window).trigger('resize');
 
})( this, jQuery );

Modified code above based on work from https://twitter.com/OzzyR and https://twitter.com/brianbourn