How to check if the URL contains a given string?

You would use indexOf like this:

if(window.location.href.indexOf("franky") != -1){....}

Also notice the addition of href for the string otherwise you would do:

if(window.location.toString().indexOf("franky") != -1){....}

You need add href property and check indexOf instead of contains

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script type="text/javascript">
  $(document).ready(function() {
    if (window.location.href.indexOf("franky") > -1) {
      alert("your url contains the name franky");
    }
  });
</script>

if (window.location.href.indexOf("franky") != -1)

would do it. Alternatively, you could use a regexp:

if (/franky/.test(window.location.href))