一道面试题让你彻底掌握JS中的EventLoop（头条）

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");
      // 有微任务和宏任务，先执行微任务，第一个进微任务先执行
      // 输出顺序  async1 start -->async2-->promise1-->script end-->async1 end-->promise2-->setTimeout

事件绑定，定时器宏任务
promise,async和await微任务,