<script>
let pageStart = (new Date()).getTime();

window.addEventListener('load', function (event) {

    let pageEnd = (new Date()).getTime();

    setTimeout(function() {
        let browser = new FormData();

        browser.append('conn_type', navigator.connection.type);
        browser.append('conn_downlink', navigator.connection.downlink);
        browser.append('conn_rtt', navigator.connection.rtt);

        browser.append('device_lang', navigator.languages);
        browser.append('device_platform', navigator.platform);
        browser.append('device_vendor', navigator.vendor);

        let perfData = window.performance.timing;
        browser.append('event_complete', ((pageEnd - pageStart) / 1000).toFixed(2));
        browser.append('content_complete', ((perfData.loadEventEnd - perfData.navigationStart) / 1000).toFixed(2));
        browser.append('dns_complete', ((perfData.domainLookupEnd - perfData.domainLookupStart) / 1000).toFixed(2));

        let xhr = new XMLHttpRequest();
        xhr.open('POST', '/change-info', true);
        xhr.send(browser);

    }, 0);
});</script>