Select Random Link From Atom RSS Feed

I have this code which creates a text that redirects to a random post for a given feed URL (For blogger blogs)
<div id="myLuckyPost">
</div>
<script type="text/javascript">
function showLucky(root){ var feed = root.feed;
var entries = feed.entry || []; var entry = feed.entry[0]; for (var j = 0;
j < entry.link.length; ++j){if (entry.link[j].rel == 'alternate'){
window.location = entry.link[j].href;}}}
function fetchLuck(luck){ script = document.createElement('script');
script.src = '[URL]'; script.type = 'text/javascript';
document.getElementsByTagName('head')[0].appendChild(script);
} function feelingLucky(root){
var feed = root.feed; var total = parseInt(feed.openSearch$totalResults.$t,10);
var luckyNumber = Math.floor(Math.random()*total);luckyNumber++;
a = document.createElement('a'); a.href = '#random';
a.rel = luckyNumber; a.onclick = function(){fetchLuck(this.rel);};
a.innerHTML = 'View Random Post';
document.getElementById('myLuckyPost').appendChild(a); }
</script> <script src="[URL]">
</script>

How to use this generated random link individually as a variable. (Ex. I don't want to create a text that redirect me to the random post, I want to put it in a variable form to use it in another script). Like This:
var randompost = random post url here;