js宏任务微任务输出解析

news/2024/9/22 23:09:06/

第一种情况

javascript">      setTimeout(function () {console.log('setTimeout 1') //11 宏任务new Promise(function (resolve) {console.log('promise 1') //12 同步函数resolve()}).then(function () {console.log('promise then') //13 微任务})})async function async1() {console.log('async1 start') //2 函数调用await async2()console.log('async1 end') //7 等待async2执行完成、宏任务里的所有同步函数完成和正常输出完成后，再次获得执行机会await async3()}async function async2() {console.log('async2') //3 函数调用}async function async3() {console.log('async3') //8 函数调用}console.log('eventLoop')  //1  宏任务async1()new Promise(function (resolve) {console.log('promise 2') //4 遇到async2异步函数，处于等待状态，执行promise里的同步函数resolve()}).then(function () {console.log('promise2 then') //9 执行这个微任务})new Promise(function (resolve) {console.log('promise 4') //5 执行promise里的同步函数resolve()}).then(function () {console.log('promise4 then') //10 按照顺序，执行这个微任务})console.log('eventLoop end') //6 宏任务里的正常输出

第二种情况

javascript">      const init = async () => {setTimeout(function () {console.log('setTimeout 1') //11 宏任务new Promise(function (resolve) {console.log('promise 1') //12 同步函数resolve()}).then(function () {console.log('promise then') //13 微任务})})async function async1() {console.log('async1 start') //2 函数调用await async2()console.log('async1 end') //4 等待async2执行完成await async3()}async function async2() {console.log('async2') //3 函数调用}async function async3() {console.log('async3') //5 函数调用}console.log('eventLoop') //1  宏任务await async1() // 异步函数async1全部执行完成后才会继续往下走new Promise(function (resolve) {console.log('promise 2') //6 执行promise里的同步函数resolve()}).then(function () {console.log('promise2 then') //9 执行这个微任务})new Promise(function (resolve) {console.log('promise 4') //7 执行promise里的同步函数resolve()}).then(function () {console.log('promise4 then') //10 按照顺序，执行这个微任务})console.log('eventLoop end') //8 宏任务里的正常输出}init()