v0.10.21官方文档这样描述:

To schedule the “immediate” execution of callback after I/O events callbacks and before setTimeout and setInterval . 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.

按照道理来说，nextTick运行最快，然后到setImmediate,最后到setTimeout 。

但是从我多次运行的结果来看，事实并不是这样。nextTick最快没问题，但是每次都是setTimeout 先出现，然后setImmediate才出现。

这是为什么呢？求解答。。。