How to change href of tag on button click through javascript

Without having a href, the click will reload the current page, so you need something like this:

<a href="#" onclick="f1()">jhhghj</a>

Or prevent the scroll like this:

<a href="#" onclick="f1(); return false;">jhhghj</a>

Or return false in your f1 function and:

<a href="#" onclick="return f1();">jhhghj</a>

….or, the unobtrusive way:

<a href="#" id="abc">jhg</a>
<a href="#" id="myLink">jhhghj</a>

<script type="text/javascript">
  document.getElementById("myLink").onclick = function() {
    document.getElementById("abc").href="xyz.php"; 
    return false;
  };
</script>