[removed] Is it ok to call cleartimeout before settimeout?

Question

I have a function that sets a timer, and calls itself back upon expiration of the timer.

What I\'d like to know is if it is bad practice to clear the timer at the top o

Answer 1

Yes you can call clearTimeout(timer), but there are some edge cases where it may cause issues.

If timer had been previously set with some other integer value, you might be killing off a completely unrelated timer.

setTimeout just returns an integer index for the timer. If you're not sure if a timer has been previously set, you could add a check before calling clearTimeout:

if (window.timer)
{
  clearTimeout(timer);
}
...
timer = setTimeout(onAir, duration);

A solution to the possible pollution of the timer variable is to use a closure:

(function(){
  var timer,
    duration;
  duration = 60000;
  window.onAir = function onAir(){
    ...code...
    if (timer){
      clearTimeout(timer);
    }
    timer = setTimeout(onAir,duration);
  };
});