How to change the style of a NAV element when it's selected with JavaScript only?

I want to style a navigation anchor element whenever an user clicks on it and it loads a page to be different. I want that particular selected page to have the style: #active{ color: red; border-bottom: 3px solid red; }.

I managed to almost achieve that by using an "onclick" event on each anchor element inside the div with class menu; that "onclick" event calls for a function named changeStyle(this) and gives as an argument the current anchor as an object.

In the javascript file I have created the following function:

function changeStyle(sender) {
    var anchorsArray = document.querySelectorAll('.menu a');

    switch (sender.innerHTML) {
        case "ACASA":
            anchorsArray[0].setAttribute("id", "active");
            anchorsArray[1].removeAttribute("id");
            anchorsArray[2].removeAttribute("id");
            anchorsArray[3].removeAttribute("id");
            anchorsArray[4].removeAttribute("id");
            anchorsArray[5].removeAttribute("id");
            break;
        case "ECHIPA":
            anchorsArray[1].setAttribute("id", "active");
            anchorsArray[0].removeAttribute("id");
            anchorsArray[2].removeAttribute("id");
            anchorsArray[3].removeAttribute("id");
            anchorsArray[4].removeAttribute("id");
            anchorsArray[5].removeAttribute("id");
            break;
        case "SERVICII SI TARIFE":
            anchorsArray[2].setAttribute("id", "active");
            anchorsArray[0].removeAttribute("id");
            anchorsArray[1].removeAttribute("id");
            anchorsArray[3].removeAttribute("id");
            anchorsArray[4].removeAttribute("id");
            anchorsArray[5].removeAttribute("id");
            break;
        case "GALERIE FOTO":
            anchorsArray[3].setAttribute("id", "active");
            anchorsArray[0].removeAttribute("id");
            anchorsArray[1].removeAttribute("id");
            anchorsArray[2].removeAttribute("id");
            anchorsArray[4].removeAttribute("id");
            anchorsArray[5].removeAttribute("id");
            break;
        case "OFERTE":
            anchorsArray[4].setAttribute("id", "active");
            anchorsArray[0].removeAttribute("id");
            anchorsArray[1].removeAttribute("id");
            anchorsArray[3].removeAttribute("id");
            anchorsArray[2].removeAttribute("id");
            anchorsArray[5].removeAttribute("id");
            break;
        case "CONTACT":
            anchorsArray[5].setAttribute("id", "active");
            anchorsArray[0].removeAttribute("id");
            anchorsArray[1].removeAttribute("id");
            anchorsArray[3].removeAttribute("id");
            anchorsArray[4].removeAttribute("id");
            anchorsArray[2].removeAttribute("id");
            break;
        default:
            break;
    }
}

and this changeStyle(sender) function verifies each object's .innerHTML value and if it matches it with a case it changes the style of that anchor element. Everything is ok here, but if I try to link other pages to the menu this function won't work properly when the new page is loaded and I don't have any ideea how to achieve this using just JavaScript with no jQuery or PHP.

What I'm trying to say is if I change the "href" attribute of each <a> element from "#" to let's say "index.html" the page will reload when I click on it, but the function will not be called anymore and the style will be reset to it's default behavior.

Bellow is the DEMO of what I'm trying to achieve : https://jsfiddle.net/bookw0rm/18x0puwm/11/

Try changing the <a href="#" class="butoane butonAcasa" onclick="changeStyle(this);">ACASA</a> to <a href="index.html" class="butoane butonAcasa" onclick="changeStyle(this);">ACASA</a> in the fiddle DEMO to see what I'm trying to achieve and to see what doesn't work for me because it will help you understand my exact need.

I don't mind if you show me other ways to achieve this thing using JavaScript only ... it only matters to me to achieve it by using JavaScript only with NO jQuery or PHP. Thanks in advance.