Run javascript on specific URL load

I want to run javascript on specific URL load, below is my code. It only shows an alert on the home page, not on the URL I have a condition on i.e. https://www.example.com/cart it gives an alert message on the home page only.

<script type="text/javascript">
    var currURL = window.location.href;

   function codeAddress() {

     if (currURL = 'https://www.example.com/cart'){
            alert('We are not shipping to countries that are not listed in shipping country!');
     }
    }
  window.onload = codeAddress;
        </script>