php - Call javascript function on every second ( nearly 1800 seconds ) setTimeout & setInterval having lagging issue

Question

I want to show login popup before 1 minute of session timeout.Max session idle timeout value is 1800 seconds ( 30 mins. ) So I used one counter variable like idlecount. Using setInterval() I am incrementing that variable value. So now when variable value is 1740 ( i.e my idle session timeout value 1800 - 60 sec. ) then I will show login popup ( Having 2 buttons (1) Keep me sign in (2) Sign out ). The issue is that setInterval() not properly maintaing the value of variable idlecount. Due to that login popup not working properly.

Answer 1

You should not use a timeout or setinterval when you want to rely on real expiring time as them are not reliable. Also, notice that a refresh cancel the setTimeout/setInterval. Instead you should use a setInterval that check every x seconds if the session has expired checking it against current Date() object.

Example:

setInterval(function(){
  var decodedToken = localStorage.getItem('user_token');
  if (decodedToken.exp < new Date().getTime()/1000) {
    // Token is expired
  }
}, 3000);