代码规范

异步

callback

callback 进行错误处理

// ❌
function callback(err, data) {
  console.log(data);
}

// ✅
function callback(err, data) {
  if (err) {
    console.log(err);
    return;
  }

  console.log(data);
}

promise

Promise 不使用 async

// ❌
new Promise(async (resolve, reject) => {});

// ✅
new Promise((resolve, reject) => {});

Promise 中不使用 return

// ❌
new Promise((resolve, reject) => {
  return result;
});

// ✅
new Promise((resolve, reject) => {
  resolve(result);
});

reject 抛出 error

// ❌
Promise.reject("An error occurred");

// ✅
Promise.reject(new Error("An error occurred"));

总是使用 catch

// ❌
myPromise().then(() => {});

// ✅
myPromise()
  .then(() => {})
  .catch(() => {});

await/async

避免 await 结合使用的赋值操作

// ❌
let totalPosts = 0;
async function getPosts(userId) {
  const users = [
    { id: 1, posts: 5 },
    { id: 2, posts: 3 },
  ];
  await sleep(Math.random() * 1000);
  return users.find((user) => user.id === userId).posts;
}
async function addPosts(userId) {
  totalPosts += await getPosts(userId);
}
await Promise.all([addPosts(1), addPosts(2)]);
console.log("Post count:", totalPosts); // 3 or 5

// ✅
let totalPosts = 0;
async function getPosts(userId) {
  const users = [
    { id: 1, posts: 5 },
    { id: 2, posts: 3 },
  ];
  await sleep(Math.random() * 1000);
  return users.find((user) => user.id === userId).posts;
}
async function addPosts(userId) {
  const posts = await getPosts(userId);
  totalPosts += posts; // variable is read and immediately updated
}
await Promise.all([addPosts(1), addPosts(2)]);
console.log("Post count:", totalPosts);

避免使用 return await

// 👎
async () => {
  try {
    return await getUser(userId);
  } catch (error) {
    // Handle getUser error
  }
};

// 👍
async () => {
  try {
    const user = await getUser(userId);
    return user;
  } catch (error) {
    // Handle getUser error
  }
};

循环中不使用 await

// ❌
for (const url of urls) {
  const response = await fetch(url);
}

// ✅
const responses = [];
for (const url of urls) {
  const response = fetch(url);
  responses.push(response);
}

await Promise.all(responses);