<!DOCTYPE html>
<html lang="en-US">
<body>
<a>Learn jQuery</a>
<p>Click on the button to set 'href' for the above anchor tag.</p>
<button onclick="myFunction()">Click Me</button>
<script>
var elem = document.getElementsByTagName("a")[0];
function myFunction(){
elem.setAttribute("href", "/jquery")
}
</script> </body>
</html>