Why does setTimeout() "break" for large millisecond delay values?

Question

I came across some unexpected behavior when passing a large millisecond value to setTimeout(). For instance,

setTimeout(some_callback, Number.MAX_VALUE);

and

setTimeout(some_callback, Infinity);

both cause some_callback to be run almost immediately, as if I'd passed 0 instead of a large number as the delay.

Why does this happen?

Answer 1

This is due to setTimeout using a 32 bit int to store the delay so the max value allowed would be

2147483647

if you try

2147483648

you get your problem occurring.

I can only presume this is causing some form of internal exception in the JS Engine and causing the function to fire immediately rather than not at all.

HTH

OneSHOT

Answer 2

Number.MAX_VALUE

is actually not an integer. The maximum allowable value for setTimeout is likely 2^31 or 2^32. Try

parseInt(Number.MAX_VALUE) 

and you get 1 back instead of 1.7976931348623157e+308.