async function async1() {

      console.log("async1 start");

      await async2();

      console.log("async1 end");

    }

    async function async2() {

      console.log("async2");

    }

    console.log("start");

    setTimeout(() => {

      console.log("timeout");

    }, 0);

    async1();

    console.log("processing");

    new Promise((resolve, reject) => {

      for (let index = 0; index < 2; index++) {

        console.log(index);

        resolve();

      }

    })

      .then3(function () {

        console.log("promise1");

      })

      .then4(() => {

        console.log("promise2");

      });

    console.log("end");
   

 function async11() {

      return new Promise((resolve) => {

        console.log("async11 start");

        resolve(async2());

      }).then2(() => {

        console.log("async11 end");

      });

    }

    // async2 的promise写法为

    function async22() {

      return new Promise((resolve) => {

        resolve(console.log("async22"));

      }).then1(() => {

        console.log("async22 micro"); //这里是校验微任务执行了,题目中为空语句

      });

    }