<ul class="popup__features">
<li class="feature"></li>
<li class="feature"></li>
<li class="feature"></li>
<li class="feature"></li>
<li class="feature"></li>
<li class="feature"></li>
</ul>
var featuresArray = ['feature--wifi', 'feature--dishwasher', 'feature--parking', 'feature--washer', 'feature--elevator', 'feature--conditioner'];
var el = cardElement.querySelectorAll('ul li.feature');
for (var i = 0; i < el.length; i++) {
el.classList.add(featuresArray);
}