How do I compare dates in Javascript?

Question

I have the following situation:

I have a certain function that runs a loop and does stuff, and error conditions may make it exit that loop. I want to be able to check whether the loop is still running or not.

For this, i'm doing, for each loop run:

LastTimeIDidTheLoop = new Date();

And in another function, which runs through SetInterval every 30 seconds, I want to do basically this:

if (LastTimeIDidTheLoop is more than 30 seconds ago) {
  alert("oops");
}

How do I do this?

Thanks!

Answer 1

JS date objects store milliseconds internally, subtracting them from each other works as expected:

var diffSeconds = (new Date() - LastTimeIDidTheLoop) / 1000; 
if (diffSeconds > 30)
{
  // ...
}

Answer 2

what about:

newDate = new Date()
newDate.setSeconds(newDate.getSeconds()-30);
if (newDate > LastTimeIDidTheLoop) {
  alert("oops");
}