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I'm writing a web app that needs to send notifications. It checks 12 different things every 30 seconds and if one of them meets the criteria it should send a notification; it then shouldn't send another notification until the next 30 minute (on the hour and half past the hour) interval. How do you check if a notification has already been sent and not to send it again? I thought this was done via tags but two notifications with the same tag will still pop-up, the second will just replace the first.

The function used to generate the notification is 

function randomNotification(whoisit, tagtoPass) {

    var message = whoisit + " is getting a notification";
    var options = {
        body: message,
        icon: 'logo.png',
        tag: tagtoPass,
    }

    var n = new Notification('Website Says:',options);
    setTimeout(n.close.bind(n), 5000);
  }

That function is called from another script that is loaded via Ajax every 30 seconds. That script checks the database to see if one of the 12 things is in a state that requires a notifications then calls the function and passes the name and a unique tag for that 30 minute interval.

Also I've noticed with this code, which was based on the developer docs from Mozilla on Notifications API, doesn't add the notification to the OS X Notification Centre.

Flatlyn
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    You can use a Redis lock as described in [this post](http://blog.pushpad.xyz/2017/07/how-to-throttle-notifications-to-user-and-reduce-cost/) – collimarco Oct 08 '17 at 19:05

1 Answers1

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Have you considered using a flag in localStorage to store the time when the last notification was sent?

Let's say that you store the time when you send the first notification, then check it again and if it's old enough you send another one and update that flag.

localStorage data will stay even if you refresh the web page.

Example:

localStorage.setItem("last_notification", timestamp)
localStorage.getItem("last_notification")

Reference: https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage

Felipe
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    I had considered that but had assumed that wasn't the correct way to use notifications and that I should be using some kinda of native notifications API solution – Flatlyn Oct 08 '17 at 01:44