var a = document.getElementsByClassName('product-card-big__descr')

for(var b = 0, c = a.length; b < c; b++) {
var d = a[b];

d.children[0].innerHTML = d.children[0].getAttribute('data-special-price');
d.children[1].children[0].innerHTML = d.children[1].children[0].getAttribute('data-saving-percent');

}