onclick not working since move from HTML to WP

I would try separating the html from the javascript. i.e. not using “onclick” in html but instead using addEventListener.

<a href="javascript:document.searchform.submit();"  class="btn_reserve">Reserve Now!</a>

<script>
    document.querySelector('.btn_reserve').addEventListener("click", function(e) {

        // it seems like this line won't return a URL and will instead submit the form. 
        // I would double check it.
        var url = document.searchform.submit(); 

        goog_report_conversion(url);
    });
</script>