Code for landing page

<script>
    function getUrlParams() {
        const params = new URLSearchParams(window.location.search);
        const allowedParams = {
            'campaign_id': 'campaign_id_fb',
            'adset_id': 'adset_id',
            'ad_id': 'ad_id',
            'campaign_name': 'campaign_name_fb',
            'adset_name': 'adset_name',
            'ad_name': 'ad_name',
            'placement': 'placement',
            'site_source_name': 'site_source_name',
            'fbclid': 'fbclid',
            'pixel_id': 'pixel_id',
            'access_token': 'access_token'
        };
        const result = {};

        Object.keys(allowedParams).forEach(param => {
            if (params.has(param)) {
                result[allowedParams[param]] = params.get(param);
            }
        });

        return result;
    }

    function createEventSourceUrl() {
        const protocol = window.location.protocol;
        const host = window.location.host;
        const path = window.location.pathname;

        return `${protocol}//${host}${path}`;
    }

    function updateLinks(params) {
        document.querySelectorAll('a').forEach(link => {
            const url = new URL(link.href);
            Object.keys(params).forEach(key => url.searchParams.set(key, params[key]));
            link.href = url.toString();
        });
    }

    function addExternalIdFromLocalStorage() {
        const subid = localStorage.getItem('subId');
        if (subid) {
            updateLinks({ external_id: subid });
            clearInterval(checkStorageInterval); // Остановить проверку, если _subid найден
        }
    }

    // Инициализация
    const params = getUrlParams();
    if (Object.keys(params).length > 0) {
        params.event_source_url = createEventSourceUrl();
        updateLinks(params);
    }

    // Проверка на появление _subid в localStorage каждые 500 мс
    const checkStorageInterval = setInterval(addExternalIdFromLocalStorage, 100);
</script>