JavaScript - actualizar en tiempo real

<button>Notify me!</button>

<script type="text/javascript">

	let NotificationOK = false;

	const notifyBtn = document.querySelector("button");

    notifyBtn.addEventListener("click", () => {

    	if(Notification.permission === "granted" && NotificationOK) {

        	const title = "Notification";

            const body = "I'm notifying you!";

            const options = {

            	body: body,

                lang: "EN",

                renotify: true

            };

            const notification = new Notification(title, options);

        }

    });

    if(!("Notification" in window)) {

    	alert("This browser does not support desktop notification!");

    } else {

    	Notification.requestPermission(function (permission) {

        	if (permission === "granted")

            	NotificationOK = true;

        });

    }

</script>