Robust Error Handling in Node.js

Proper error handling is crucial for building stable and reliable Node.js applications. This guide covers best practices for handling both synchronous and asynchronous errors.

Synchronous Errors: `try...catch`

For synchronous code, the standard `try...catch` block is the way to go.

try {
  const data = JSON.parse(invalidJsonString);
} catch (error) {
  console.error('Failed to parse JSON:', error);
}

Asynchronous Errors: Promises and `async/await`

For Promises, you can chain a `.catch()` block. With `async/await`, you can use `try...catch` just like with synchronous code.

// async/await
app.get('/data', async (req, res) => {
  try {
    const data = await fetchDataFromDb();
    res.json(data);
  } catch (error) {
    res.status(500).send('Database error');
  }
});

Centralized Error Handling in Express

The best practice in an Express application is to create a centralized error-handling middleware. This middleware is defined with four arguments `(err, req, res, next)`.

// This middleware should be the last one in your app.use() stack
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});