Capture a Querystring from URL and place into site cookies using Javascript/JQuery in WordPress

Solution:

You can do this by javascripts. first you have to get query string from URL and then have to save in cookie using this document.cookie = name + "=" + (value || "") + expires + "; path=/";

<script type="text/javascript">
    // self executing function here
    (function() {
       
        function getParameterByName(name, url = window.location.href) {
            name = name.replace(/[\[\]]/g, '\\$&');
            var regex = new RegExp('[?&]' + name + '(=([^&#]*)|&|#|$)'),
                results = regex.exec(url);
            if (!results) return null;
            if (!results[2]) return '';
            return decodeURIComponent(results[2].replace(/\+/g, ' '));
        }

        function setCookie(name,value,days) {
        
            var expires = "";
            if (days) {
                var date = new Date();
                date.setTime(date.getTime() + (days*24*60*60*1000));
                expires = "; expires=" + date.toUTCString();
            }
            document.cookie = name + "=" + (value || "")  + expires + "; path=/";
        }

        function getCookie(name) {
            var nameEQ = name + "=";
            var ca = document.cookie.split(';');
            for(var i=0;i < ca.length;i++) {
                var c = ca[i];
                while (c.charAt(0)==' ') c = c.substring(1,c.length);
                if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
            }
            return null;
        }

        function eraseCookie(name) {   
            document.cookie = name +'=; Path=/; Expires=Thu, 01 Jan 1970 00:00:01 GMT;';
        }

        // query string: ?ref=hotelname&loc=townname
        var ref = getParameterByName('ref'); 
        var loc = getParameterByName('loc'); 
        
        if( ref !== null ){
            setCookie( 'ref', ref, 365 );
        }
        if( loc !== null ){
            setCookie( 'loc', loc, 365 );
        }

    })();
</script>