How to send a browser notification when a specific time occurs?

I'm creating a to-do app with MEAN stack. Input will be to-do text and to-do time, which will be stored in database. This is my code to fetch client browser time and send notification with that time. But what I need is, notification should be send when the time stored in database occurs. How I can do that?

<script>
        Notification.requestPermission().then(function(result) {
        var time = new Date();
        var bhours = time.getHours();
        var bminutes = time.getMinutes();
        var btime = bhours + ':' + bminutes;
        var notification = new Notification(btime);
      });
</script>

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