Display online offline connection status using JavaScript

<script type="text/javascript">
    window.onload = function () {
        setInterval(function () {
            if (!navigator.onLine) {
                alert("You are not connected to Internet, ensure you're not in airplane mode. \n\nYour internet signal may be week. \n\nPlease connect to internet and try again.");
            }
        }, 2000);
    }
</script>