1

console.log('script start');
setTimeout(function () {
    console.log('setTimeout');
}, 0);
new Promise(resolve => {
    console.log('Promise');
    resolve();
}).then(function () {
    setTimeout(function () {
        console.log('setTimeout in promise1');
    }, 0);
    console.log('promise1');
}).then(function () {
    console.log('promise2');
});
console.log('script end');
// script start
// Promise
// script end
// promise1
// promise2
// setTimeout
// setTimeout in promise1

2

async function async1() {
  console.log('async1 start');
  await async2();
  console.log('async1 end');
}
async function async2() {
console.log('async2');
}
console.log('script start');
setTimeout(function() {
  console.log('setTimeout');
}, 0)
async1();
new Promise(function(resolve) {
  console.log('promise1');
  resolve();
}).then(function() {
  console.log('promise2');
});
console.log('script end');
// script start
// async1 start
// async2
// promise1
// script end
// async1 end
// promise2
// setTimeout

特别注意**async2**执行的顺序， await的函数内部 其实是同步执行的，相当于在promise里面。

async function async1() {
    console.log('async1 start');
    await async2();
    console.log('async1 end');
}
/ ==
async function async1() {
    console.log('async1 start');
    Promise.resolve(async2()).then(() => {
                console.log('async1 end');
        })
}

3

async function async1() {
  console.log("async1 start");
  await async2();
  setTimeout(function () {
    console.log("setTimeout1");
  }, 0);
}
async function async2() {
  setTimeout(function () {
    console.log("setTimeout2");
  }, 0);
}
console.log("script start");
setTimeout(function () {
  console.log("setTimeout3");
}, 0);
async1();
new Promise(function (resolve) {
  console.log("promise1");
  resolve();
}).then(function () {
  console.log("promise2");
});
console.log("script end");
// script start
// async1 start
// promise1
// script end
// promise2
// setTimeout3
// setTimeout2
// setTimeout1

4

async function a1() {
  console.log("a1 start");
  await a2();
  console.log("a1 end");
}
async function a2() {
  console.log("a2");
}
console.log("script start");
setTimeout(() => {
  console.log("setTimeout");
}, 0);
Promise.resolve().then(() => {
  console.log("promise1");
});
a1();
let promise2 = new Promise((resolve) => {
  resolve("promise2.then");
  console.log("promise2");
});
promise2.then((res) => {
  console.log(res);
  Promise.resolve().then(() => {
    console.log("promise3");
  });
});
console.log("script end");
// script start
// a1 start
// a2
// promise2
// script end
// promise1
// a1 end
// promise2.then
// promise3
// setTimeout

5

console.log("start");
setTimeout(() => {
  console.log("children2");
  Promise.resolve().then(() => {
    console.log("children3");
  });
}, 0);
new Promise((resolve, reject) => {
  console.log("children4");
  setTimeout(() => {
    console.log("children5");
    resolve("children6");
  }, 0);
}).then((res) => {
  console.log("children7");
  setTimeout(() => {
    console.log(res);
  }, 0);
});
//start
//children4
//childern2
//childern3
//childern5
//childern7
//children6

6

const p = () => {
  return new Promise((resolve, reject) => {
    const p1 = new Promise((resolve, reject) => {
      setTimeout(() => {
        resolve(1);
      }, 0);
      //   resolve(2);
    });
    p1.then((res) => {
      console.log(res);
    });
    console.log(3);
    resolve(4);
  });
};
p().then((res) => {
  console.log(res);
});
console.log("end");
// 3
// end
// 4
// 1