Promise

.await是包装.then(onFulfilled)（成功回调）和错误抛出的语法糖 .catch是.then(null, onRejected)的语法糖

// 假设 fetchUser 和 fetchPosts 同样返回 Promise
 
async function getUserAndPosts(id) {
  try {
    const user = await fetchUser(id); // 等待 fetchUser Promise 解决
    console.log("用户:", user.name);
 
    const posts = await fetchPosts(user.id); // 等待 fetchPosts Promise 解决
    console.log("帖子:", posts);
  } catch (error) {
    console.error("发生错误:", error);
  } finally {
    console.log("操作完成");
  }
}
 
getUserAndPosts(123);

老版本处理

then、catch、finally

// 假设 fetchUser 和 fetchPosts 都返回 Promise
function fetchUser(id) {
  return new Promise(resolve => setTimeout(() => resolve({ id, name: "哲予" }), 500));
}
 
function fetchPosts(userId) {
  return new Promise(resolve => setTimeout(() => resolve([`Post 1 for ${userId}`, `Post 2 for ${userId}`]), 700));
}
 
fetchUser(123)
  .then(user => {
    console.log("用户:", user.name);
    return fetchPosts(user.id); // 返回一个新的 Promise
  })
  .then(posts => {
    console.log("帖子:", posts);
  })
  .catch(error => {
    console.error("发生错误:", error);
  })
  .finally(() => {
    console.log("操作完成");
  });