【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
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？
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