How to make a random link through Javascript/HTML [duplicate]

I am trying to create a script that allows me to display a hyperlink that redirects the user to a random url selected out of four sites. So far I have created an array for the sites, and a function that attempts to generate the random url. For my purpose it is important for the output ("Click to go to a random site") is not a button, but a simple (clickable) string.

When running the code I get a reference error "link is not defined (on line 18)". I thought that I had defined link in the code with var link = 'http://' + links[randIdx];, so I am not entirely sure why I am getting this error and how to fix it.

Anyone that could take a look at my code

<a href="javascript:openSite()">Click to go to a random site</a>
<script>
function openSite() {
var links = [
              "google.com",
              "youtube.com",
              "reddit.com",
              "apple.com"]

            openSite = function() {
              // get a random number between 0 and the number of links
              var randIdx = Math.random() * links.length;
              // round it, so it can be used as array index
              randIdx = parseInt(randIdx, 10);
              // construct the link to be opened
              var link = 'http://' + links[randIdx];
              };
              
    return link;
    
    document.getElementById("link").innerHTML = openSite();
}
</script>