is setTimeout/clearTimeout expensive?

Question

I have something like the following:

var myTimeout;
function delayStuffUntil( when ){ 
  if( myTimeout) clearTimeout( myTimeout );
  myTimeout = setTimeout( stuff, when - Date.now() );
}

delayStuffUntil is going to get called a good deal, and it's likely that it will get called with the same value of when several times in a row.

Is setTimeout/clearTimeout expensive enough that I should bother checking the current when against my last value of when (and only change timers if different)?

I thought about doing it, but the truth is that when is a bit more fiddly to compare, and I figured premature optimization is the root of all evil, so I might be making work when I didn't need to.

Answer 1

setTimeout and clearTimeout by themselves aren't very expensive.

It's really the function "stuff" is what you have to worry about.

If stuff takes a long time to run then it might block the UI if it gets called too often.