How to check if the URL contains a given string?

custom.js

<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("checkout/?add-to-cart=1375&quantity=1") > -1) {
       titleClass = document.querySelector(".find_class_to_add_new_class");
       titleClass.classList.add("display-none-info");
    }
  });
</script>