scott好，

const { readFile, readFileSync } = require('fs')


setImmediate(() =>  console.log('[阶段3.immediate] immediate 回调1'))
setImmediate(() =>  console.log('[阶段3.immediate] immediate 回调2'))
setImmediate(() =>  console.log('[阶段3.immediate] immediate 回调3'))

Promise.resolve()
  .then(() => {
    console.log('[...等待切入下一个阶段] promise 回调 1')
    setImmediate(() => console.log('[阶段3.immediate] promise 回调1 增加的 immediate 回调4'))
  })

readFile('../package.json', 'utf-8', data => {
  console.log('[阶段2...IO 回调] 读文件回调1')

  readFile('../package-lock.json', 'utf-8', data => {
    console.log('[阶段2...IO 回调] 读文件回调2')
    setImmediate(() => console.log('[阶段3.immediate] 读文件回调2 增加的 immediate 回调4'))
  })

  setImmediate(() =>  {
    console.log('[阶段3.immediate] immediate 回调5')

    Promise.resolve()
      .then(() => {
        console.log('[...等待切入下一个阶段] promise 回调 2')

        process.nextTick(() => {
          console.log('[...待切入下一个阶段] promise 回调2增加的 nextTick 回调5')
        })
      })
      .then(() => {
        console.log('[...等待切入下一个阶段] promise 回调 3')
      })
  })

  setImmediate(() =>  {
    console.log('[阶段3.immediate] immediate 回调6')

    process.nextTick(() => {
      console.log('[...待切入下一个阶段] immediate 回调6 nextTick 回调7')
    })
    console.log('[...待切入下一个阶段] 这块正在同步阻塞的读一个大文件')
    const video = readFileSync('../package-lock.json', 'utf-8')
    process.nextTick(() => {
      console.log('[...待切入下一个阶段] immediate 回调6 nextTick 回调8')
    })

    readFile('../package.json', 'utf-8', data => {
      console.log('[阶段2...IO回调] 读文件回调3')

      setImmediate(() => console.log('[阶段3.immediate] 读文件回调3 增加的 immediate 回调6'))

      setTimeout(() => console.log('[阶段1...定时器] 读文件回调3 增加的 定时器回调8'), 0)
    })
  })

  process.nextTick(() => {
    console.log('[...待切入下一个阶段] 读文件 回调1 增加的 nextTick 回调6')
  })

  setTimeout(() => console.log('[阶段1...定时器] 定时器 回调5'), 0)
  setTimeout(() => console.log('[阶段1...定时器] 定时器 回调6 '), 0)
})

setTimeout(() => console.log('[阶段1...定时器] 定时器 回调1'), 0)
setTimeout(() => {
  console.log('[阶段1...定时器] 定时器 回调2')

  process.nextTick(() => {
    console.log('[...待切入下一个阶段] nextTick 回调5')
  })
}, 0)
setTimeout(() => console.log('[阶段1...定时器] 定时器 回调3'), 0)
setTimeout(() => console.log('[阶段1...定时器] 定时器 回调4'), 0)

process.nextTick(() => console.log('[...待切入下一个阶段] nextTick 回调1'))
process.nextTick(() => {
  console.log('[...待切入下一个阶段] nextTick 回调2')
  process.nextTick(() => console.log('[...待切入下一个阶段] nextTick 回调4'))
})
process.nextTick(() => console.log('[...待切入下一个阶段] nextTick 回调3'))

在执行timers阶段70行~79行中的这个打印的setTimout中有一个nextTick（[...待切入下一个阶段] nextTick 回调5，执行完这个后

就该进入到第二阶段，但是为什么图中，我画框的打印中，第三阶段的immediate会比异步IO先执行呢？同样的，后面的一个框也是这样的问题，我没有想明白这是为什么？