network-online-and-up-js-refresh-test.js

// browser kiosk web app refresh via Javascript
// this test if network is up and browser is online
function refresh() {
    // network is up (but this does not mean there is a live internet connection)
    if (navigator.onLine == true) {
        $.ajax({
            // try to fetch non-existent 404 URL that is not cached (include timestamp)
            url: '../X24S54d4wqewq887_madeup_url_online_test' + new Date().getTime(),
            // timeout after 3 seconds
            timeout: 3000,
            // always error, but
            error: function(xhr) {
                console.log(xhr.status)
                // 404 actually means we have received live connection status back from server !
                if (xhr.status == 404) {
                    window.location.reload(true);
                } else {
                    // no response from server, let's retry in 6 seconds
                    setTimeout(refresh, 6000);
                    // failed to reload
                }
            }
        });
    }
}