Andrei Antanovich

<a href="#" class="item">Item1</a>
<a href="#" class="item">Item2</a>
<a href="#" class="item">Item3</a>

.active {
  color: green;
}

var els = document.querySelectorAll('.item');
[].forEach.call(els, function(el, i, els) {
    el.addEventListener('click', function() {
        [].forEach.call(els, function(el) {
            if(el !== this) {
               el.classList.remove("active");
            } else {
               el.classList.add("active");
            }
        }, this);
    });
});