I have an application for organizing on-the-field employees. These employees usually go around town to complete jobs. I also have an admin panel through which I allocate different jobs to these employees.

The thing is, I need to know where each employee is at every given moment in order to be able to allocate a job based on their location (I wouldn't want to allocate a job to a tech who is 10 kilometers away).

I have a backend system which stores the current geolocation of each user and a map which displays their location. Now the last thing I need is to be able to track their location when they have closed the app or locked their phone.

My application is actually just a PWA, so I dont have any native control of the device. I have successfully registered a service-worker and added the following task:

serviceWorkerRegistration.register({
  onSuccess: () => {
    const user = JSON.parse(localStorage.getItem(KEY))?.user
    setInterval(() => {
      if (user.currentUser?._id !== undefined) {
        displayNotification(user === undefined ? "Undefined" : user.currentUser._name)
        navigator.geolocation.getCurrentPosition(e => {
          const data = new FormData()
          data.append("user", JSON.stringify({
            _id: user.currentUser._id,
            _last_lat: e.coords.latitude,
            _last_lon: e.coords.longitude
          }))
          axios.post(API_URL + '/api/user/update', data)
          .then(() => displayNotification("Data sent!"))
        }, error => {
          alert(error.code)
        })
      }
    }, 30000)
  }
});

Here is the displayNotification function:

const displayNotification = str => {
  if (Notification.permission == 'granted') {
    navigator.serviceWorker.getRegistration().then(reg => {
      reg?.showNotification(str);
    });
  }
}

This works while the user uses the application (I get both notifications - the _name of the user and Data Sent!. As soon as I exit the application, I only get the _name of the current user which means that it is not executing the fetch.

What is the reason for this? Am I doing something wrong? How do I successfully put this process in the background?