<div class="price">
  <span class="price__value">120000</span>
  <span class="price__currency"> руб.</span>
</div>
const prices = document.querySelectorAll('.price__value');

prices.forEach((price) => {
  price.textContent = parseInt(price.textContent, 10)
    .toLocaleString('ru-RU');
});

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.