<template id="tmpl">
  <div class="card">
    <h3 class="header"></h3>
    <p class="text1"></p>
    <p class="text2"></p>
  </div>
</template>

const tmpl = document.getElementById('tmpl');

const makeCard = ({ header, text1, text2 }) => {
  const card = tmpl.content.cloneNode(true);
  card.querySelector('h3').innerText = header;
  card.querySelector('p.text1').innerText = text1;
  card.querySelector('p.text2').innerText = text2;
  return card;
}

const cards = [
  { header: "header1", text1: "text 1.1", text2: "text 2.1" },
  { header: "header2", text1: "text 1.2", text2: "text 2.2" },
];

const fragment = new DocumentFragment();
cards.forEach(cardData => fragment.append(makeCard(cardData)));
document.body.appendChild(fragment);