setting cookie

<script type="text/javascript">
    $(document).ready(function(){
        var breadcrumbLink = document.getElementsByClassName("sensei-breadcrumb").childNodes, str="a"; // this sets a variable to the hyperlink inside of the breadcrumbs div that takes the user back to the module page

        breadcrumbLink.onclick = function(){
            var moduleCookie = Cookies.set('module-control', 'value');
        }; // when the user clicks on the link a cookie is made with the name module-control and a variable is called moduleCookie

        window.onbeforeunload = function () {
            var moduleCookie = Cookies.set('module-control', 'value');
        } // when the user clicks the back button a cookie is made with the name module-control and a variable is called moduleCookie

        function changediv()
        {
            if ( moduleCookie.length > 0) {
                document.getElementById("") {
                     document.getElementById("").setAttribute("id", "module1")
                }
                return Cookies.remove('module-control');
            }
        } // if moduleCookie exists get div by class and change the div id to module1
    )};
</script>