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🐛Bug of the DayBeginnerNode.js, Express, JavaScript

API Returning 500 Randomly (Async Bug You Might Be Ignoring)

~1 min read
🐛TL;DR

Random 500 errors often come from unhandled async errors that silently crash your request flow.

The Bug

Your API randomly returns 500 errors even though the code looks correct. It works sometimes, but fails unexpectedly under load or certain inputs.

Root Cause

Unhandled promise rejection inside async/await flow. When an awaited function throws an error and it's not wrapped in try/catch, Node.js fails the request and returns a generic 500 error.

The Fix

Fix:

Always wrap async logic inside try/catch and handle promise rejections properly.

Bad:

JavaScript
app.get('/data', async (req, res) => {
  const data = await fetchData(); // if this fails → 500
  res.json(data);
});

Good:

JavaScript
app.get('/data', async (req, res) => {
  try {
    const data = await fetchData();
    res.json(data);
  } catch (error) {
    console.error('Error fetching data:', error);
    res.status(500).json({ message: 'Internal Server Error' });
  }
});

Bonus Tip:
Also handle global unhandled rejections:

JavaScript
process.on('unhandledRejection', (err) => {
  console.error('Unhandled Rejection:', err);
});
APINode.jsDebuggingBackend
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