DOM Document

<!DOCTYPE html>
<html>
<head>
<title>My title</title>
</head>
<body>

<p>Click the button to change the title of the document.</p>

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

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

<script>
function myFunction() {
  document.title = "Some new title text";
  document.getElementById("demo").innerHTML = "The title of the document was changed from 'My title' to 'some new title text'. View Source to see the effect.";
}
</script>

</body>
</html>