DOM Document

<!DOCTYPE html>
<html>
<body>

<p>Click the button to check if this document has the feature HTML DOM 1.0</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
  var imp = document.implementation;
  document.getElementById("demo").innerHTML = imp.hasFeature("HTML", "1.0");
}
</script>

</body>
</html>