js中的微任务和宏任务

Promise.resolve().then(function () {
        console.log(1);
        Promise.resolve().then(function () {
          console.log(2);
        });
        Promise.resolve().then(function(){
            console.log(3);
        });
      });
      Promise.resolve().then(function(){
          console.log(4);
      })//1423

    async function fn(){
          console.log(1);
          await Promise.resolve().then(function(){
              console.log(2);
          })
          await Promise.resolve().then(function(){
              return 3;
          });
          await Promise.resolve().then(function(){
              console.log(4);
          })
      }
      fn().then(function(num){
          console.log(num);
      })//124underfined

      console.log(0);
      setTimeout(console.log(1),0);//这个里面执行的是代码块不是语句块，直接执行就OK了
      console.log(2);
      //012