This object is created internally and is returned from setImmediate().
It can be passed to clearImmediate() in order to cancel the scheduled actions.
Methods
ref():Immediate
When called, requests that the Node.js event loop not exit so long as the Immediate is active.
Calling immediate.ref() multiple times will have no effect.
By default, all Immediate objects are "ref'ed", making it normally unnecessary to call immediate.ref()
unless immediate.unref() had been called previously.