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);
}

function getConfig() {
  const raw = localStorage.getItem('config');
  return raw ? JSON.parse(raw) : {};
}

async function transfer(db, fromId, toId, amount) {
  await db.execute(
    'UPDATE accounts SET balance = balance - ? WHERE id = ?',
    [amount, fromId]
  );
  await db.execute(
    'UPDATE accounts SET balance = balance + ? WHERE id = ?',
    [amount, toId]
  );
}

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

function processItem(item) {
  console.log('START PROCESS', item);
  doHeavyWork(item);
  console.log('END PROCESS', item);
}

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

async function fetchAll(urls) {
  const promises = urls.map(url => fetch(url));
  return Promise.all(promises);
}

async function updateStatuses(users) {
  for (const user of users) {
    await fetch('/api/status', {
      method: 'POST',
      body: JSON.stringify({ id: user.id, status: 'active' })
    });
  }
}

function renderDashboard(userId) {
  const stats = calculateAllStats(userId); // 重い処理
  return buildHtml(stats);
}