Table of Contents

• Timers
  • setTimeout(callback, delay, [arg], [...])
  • clearTimeout(timeoutId)
  • setInterval(callback, delay, [arg], [...])
  • clearInterval(intervalId)
  • unref()
  • ref()
  • setImmediate(callback, [arg], [...])
  • clearImmediate(immediateId)

Timers#

Stability: 5 - 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 timeoutId 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(timeoutId)#

Prevents a timeout from triggering.

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

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

clearInterval(intervalId)#

Stops a 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 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. Returns an immediateId for possible use with clearImmediate(). Optionally you can also pass arguments to the callback.

Immediates are queued in the order created, and are popped off the queue once per loop iteration. This is different from process.nextTick which will execute process.maxTickDepth queued callbacks per iteration. setImmediate will yield to the event loop after firing a queued callback to make sure I/O is not being starved. While order is preserved for execution, other I/O events may fire between any two scheduled immediate callbacks.

clearImmediate(immediateId)#

Stops an immediate from triggering.