How to make the function of showing reminders at a certain date and time?

Question

Node.js

Good afternoon.
I am learning React and Node. As a practice, I decided to try to write a simple application with a to-do list (like many novice developers).

I decided, in addition to the list itself, to add the function of showing business reminders.
How it should work: The user sets when to be reminded of the task. At the specified time and date, a reminder appears in a separate section on the site.

But I don't even know how to approach this task.
Please advice on how to implement this feature. Maybe there are links to lessons that describe the solution of a similar problem (in Russian or English).

Answer 1

if(!notificationShown && Date.now() < userNotificationTime) {
  showNotification();
}