Timers Node.js v4.2.6 Manual & Documentation

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# Timers#

    Stability: 3 - Locked

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

## clearImmediate(immediateObject)#

Stops an immediate from triggering.

## clearInterval(intervalObject)#

Stops an interval from triggering.

## clearTimeout(timeoutObject)#

Prevents a timeout from triggering.

## 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 `ref`d calling `ref` again will have no effect.

Returns the timer.

## 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.

## 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.

To follow browser behavior, when using delays larger than 2147483647 milliseconds (approximately 25 days) or less than 1, Node.js will use 1 as the `delay`.

## 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.

To follow browser behavior, when using delays larger than 2147483647 milliseconds (approximately 25 days) or less than 1, the timeout is executed immediately, as if the `delay` was set to 1.

## 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 `unref`d 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.

Returns the timer.