Simple page changing mechanizm, Vanilla JS http://vanilla-js.com/ Suitable for small single page applications.

page-changer.js

/*
 * Let's assume that <div> containers with text have class="page" and id=page name + "Text". 
 * And the menu <a> links-switchers have class "menuItem" and id=page name + "Item".
 *
 * This script applies class "active" to selected page by observing window.location.href,
 * with "about" as default page. 
 *
 * demo: http://audioservice.pro/
 *
 * 
 */
var pages = document.getElementsByClassName("page");
var menuItems = document.getElementsByClassName("menuItem");
var pagesCount = pages.length; 

function showPage(page) {

	var i = pagesCount - 1;
	var itemFound = false;
		
	for(; i >= 0; i--) {
	
		if(pages[i].id != page + "Text") {
			pages[i].classList.remove("active");
		} else {
			pages[i].classList.add("active");

		}
	 
		if(menuItems[i].id != page + "Item") {
			menuItems[i].classList.remove("active");
		} else {
			menuItems[i].classList.add("active");
			itemFound = true;
		}
	}

	if(!itemFound)	{
		showPage("about")	;

	}
}

var href;

function listenHref() {

		if (href != window.location.href) {

				href = window.location.href;
				var page = href.match("#[A-z]+");

				if (page) {
						page = page[0].slice(1);
				}
				
				showPage(page || "about");
		}

		clearTimeout(timerId);
		timerId = setTimeout(listenHref, 100);
}

var timerId = setTimeout(listenHref, 100);
showPage("about");