<!DOCTYPE html>
<html>
<body>
<meta http-equiv="content-type" content="text/html">
<p>Click the button to change the value of the http-equiv attribute to refresh, and the content attribute to 30 seconds. This will refresh the document every 30 seconds.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
document.getElementsByTagName("META")[0].httpEquiv = "refresh";
document.getElementsByTagName("META")[0].content = "30";
document.getElementById("demo").innerHTML = "The document will refresh every 30 seconds.";
}
</script>
</body>
</html>