async await

 function a1() {
      return 1
    }
    function a2() {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          resolve(2)
        }, 3000);
      })
    }
    function a3() {
      return 3
    }
    async function Dosome() {
      console.log(a1());;
      console.log(await a2());;
      console.log(a3());;

    }
    Dosome()

// 执行async 函数 返回的都是 Promise 对象
    async function test1() {
      return 1
    }
    async function test2() {
      return Promise.resolve(2)
    }
    const result1 = test1()
    const result2 = test2()
    console.log(result1);
    console.log(result2);

    // Promise.then 成功的情况对应 await
    // await 后跟一个promise对象
    async function test3() {
      const p3 = Promise.resolve(3);
      p3.then(res => {
        console.log("data3", res);
      })
      const data3 = await p3
      console.log("data3", data3);
    }
    test3()
    // await 后跟一个普通值
    async function test4() {
      const data4 = await 4
      console.log("data4", data4);
    }
    test4()
    // await 后跟一个函数

    async function test5() {
      const data5 = await test1()
      console.log("data5", data5);
    }
    test5()
    // Promise.catch 成功的情况对应 try...catch
    async function test6() {
      const p6 = Promise.reject(6)
      try {

        const data6 = await p6
        console.log("data6", data6);
      } catch (e) {
        console.log("err", e);
      }
    }
    test6()