Table of Contents

• Timers
  • setTimeout(callback, delay[, arg][, ...])
  • clearTimeout(timeoutObject)
  • setInterval(callback, delay[, arg][, ...])
  • clearInterval(intervalObject)
  • unref()
  • ref()
  • setImmediate(callback[, arg][, ...])
  • clearImmediate(immediateObject)

Timers#

Stability: 3 - Locked

All of the timer functions are globals. You do not need to require() this module in order to use them.

setTimeout(callback, delay[, arg][, ...])#

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.

setInterval(callback, delay[, arg][, ...])#

To schedule the repeated execution of callback every delay milliseconds. Returns a intervalObject for possible use with clearInterval(). Optionally you can also pass arguments to the callback.

clearInterval(intervalObject)#

Stops an interval from triggering.

unref()#

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, it 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 unref 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()#

If you had previously unref()d a timer you can call ref() to explicitly request the timer hold the program open. If the timer is already refd calling ref again will have no effect.

setImmediate(callback[, arg][, ...])#

To schedule the "immediate" execution of callback after I/O events callbacks and before setTimeout and setInterval . Returns an immediateObject 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.