W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<body>
<style>
.myClass {
  color: white;
  background-color: DodgerBlue;
  padding: 20px;
  text-align: center;
  margin: 10px;
}
</style>

<h1>The template Element</h1>

<p>This example fills the web page with one new div element for each item in an array.</p>
<p>The HTML code of each div element is inside the template element.</p>

<p>Click the button below to display the hidden content from the template element.</p>

<button onclick="showContent()">Show hidden content</button>

function showContent() {
  let temp, item, a, i;
  temp = document.getElementsByTagName("template")[0];
  //get the div element from the template:
  item = temp.content.querySelector("div");
  //for each item in the array:
  for (i = 0; i < myArr.length; i++) {
    //Create a new node, based on the template:
    a = document.importNode(item, true);
    //Add data from the array:
    a.textContent += myArr[i];
    //append the new node wherever you like:
    document.body.appendChild(a);
  }
}
</script>

</body>
</html>