Timers

To schedule execution of a one-time callback after delay milliseconds. Returns a
timeoutObject for possible use with clearTimeout(). Optionally you can
also pass arguments to the callback.

It is important to note that your callback will probably not be called in exactly
delay milliseconds - Node.js makes no guarantees about the exact timing of when
the callback will fire, nor of the ordering things will fire in. The callback will
be called as close as possible to the time specified.

clearTimeout(timeoutObject)

Prevents a timeout from triggering.

clearInterval(intervalObject)

Stops an interval from triggering.

The opaque value returned by setTimeout and setInterval also has the method
timer.unref() which will allow you to create a timer that is active but if
it is the only item left in the event loop won’t keep the program running.
If the timer is already unrefd calling unref again will have no effect.

In the case of setTimeout when you you create a separate timer that
will wakeup the event loop, creating too many of these may adversely effect
event loop performance — use wisely.

ref()

To schedule the “immediate” execution of callback after I/O events
callbacks and before setTimeout and setInterval . Returns an
for possible use with clearImmediate(). Optionally you
can also pass arguments to the callback.

Callbacks for immediates are queued in the order in which they were created.
The entire callback queue is processed every event loop iteration. If you queue
an immediate from inside an executing callback, that immediate won’t fire
until the next event loop iteration.

clearImmediate(immediateObject)

Stops an immediate from triggering.