setInterval function of javascript

Question

In javascript we use setInterval functions like this.

myInteval= setInterval("func",t);

What if the execution time of "func" itself is greater than interval time t ?

I think js is single threaded. How is this achieved ??

JS is not a single thread. You can fire multiple functions in the same time — Murali Murugesan, May 09 '14 at 13:16
No java script is single threaded... when we execute js code, it can only happen from one thread at a time. — brother of my sister, May 09 '14 at 13:18
javascript is single threaded..view this post on stackoverflow http://stackoverflow.com/questions/21718774/how-is-javascript-single-threaded — Hawk, May 09 '14 at 13:18
See [here](http://javascript.info/tutorial/settimeout-setinterval) for some decision of how timers work in JS. — Matt Burland, May 09 '14 at 13:19
@murali, please read [this](http://ejohn.org/blog/how-javascript-timers-work/). — canon, May 09 '14 at 13:19

score 7 · Answer 1 · answered May 09 '14 at 13:17

7

Then it will wait until func has finished executing, check the queue of functions to run on an interval, then run it again.

See the event loop for more details.

answered May 09 '14 at 13:17

Quentin

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Will the browser drop queued functions ? as it also has limits ? if they are dropped which function will be dropped first ? – brother of my sister May 09 '14 at 13:21

score 1 · Answer 2 · answered May 09 '14 at 13:40

A few important things from this piece by John Resig:

http://ejohn.org/blog/how-javascript-timers-work/

...timer delay is not guaranteed...

Which means, it is not essential that the t that you specify will be honoured as is. It indicates a minimum time and not a guaranteed time.

Further down:

...Intervals don’t care about what is currently executing, they will queue indiscriminately, even if it means that the time between callbacks will be sacrificed...

So, effectively the func will be queued to be executed without any t delay if the queue is accumulated due to execution.

And is summarized at the end:

...Intervals may execute back-to-back with no delay if they take long enough to execute (longer than the specified delay).

setInterval function of javascript

2 Answers2