promise

let p = new Promise((resolve, reject) => {
  setTimeout(() => {
    if (Math.random() > 0.5) {
      resolve("成功");
    } else {
      reject("报错");
    }
  }, 1000);
});

p.then(data => {
  console.log(data);
}).catch(err => {
  console.log(err);
});

• 改写一波

function fn(resolve, reject) {
  setTimeout(() => {
    if (Math.random() > 0.5) {
      resolve("成功");
    } else {
      reject("报错");
    }
  }, 1000);
}

let p = new Promise(fn);

p.then(data => {
  console.log(data);
}).catch(err => {
  console.log(err);
});

router.get("/testSync", async (ctx, next) => {
  const a = await new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve("a");
    }, 1000);
  });
  ctx.body = {
    title: a
  };
});