AIでも壊れない堅牢コードへ鍛え直す！
コードレビュー道場 #3：非機能要件

let currentCount = 0;

async function handleRequest(req, res) {
  currentCount++;
  // いろいろな処理...
  res.end('count: ' + currentCount);
}

async function handler(req, res) {
  try {
    const data = await loadFromDb();
    res.end(JSON.stringify(data));
  } catch (e) {
    res.statusCode = 404;
    res.end('Not found');
  }
}

async function listOrdersWithUser(db) {
  const orders = await db.query('SELECT * FROM orders');
  for (const order of orders) {
    const rows = await db.query(
      'SELECT * FROM users WHERE id = ?',
      [order.user_id]
    );
    order.user = rows[0] ?? null;
  }
  return orders;
}

async function fetchWithRetry(url) {
  for (let i = 0; i < 2; i++) {
    try {
      const res = await fetch(url);
      if (!res.ok) throw new Error('bad status');
      return res;
    } catch (e) {
      await new Promise(r => setTimeout(r, 100));
    }
  }
  throw new Error('failed after 2 retries');
}

function calculate(pageSize) {
  return 1000 / pageSize;
}

async function loadData() {
  showLoading();
  const res = await fetch('/api/data');
  const data = await res.json();
  hideLoading();
  render(data);
}

const logs = [];

function logEvent(event) {
  logs.push({
    at: new Date().toISOString(),
    event
  });
}

// 毎分0秒に実行される
setInterval(runJob, 60 * 1000);

function runJob() {
  // 重い集計処理
}

async function fetchProfile(userId) {
  const res = await fetch(`https://api.example.com/users/${userId}`);
  if (!res.ok) {
    throw new Error('failed');
  }
  return res.json();
}

function handleClick() {
  let sum = 0;
  for (let i = 0; i < 1_000_000_000; i++) {
    sum += i;
  }
  alert(sum);
}