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【7-4】事件循环中第二阶段异步IO和第三阶段check的执行顺序的问题

//img1.sycdn.imooc.com//szimg/5ac3503000019a2411161056.jpg

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'))