How can I implement logging and error handling in my Express.js app?

How can I implement logging and error handling in my Express.js app?

You can use middleware for error handling and libraries like Winston or Morgan for logging. Would you like a code example?

Yes, please provide a code example for both logging and error handling.

Sure! Here's a simple example:

const express = require('express');
const morgan = require('morgan');
const app = express();

// Logging middleware
app.use(morgan('combined'));

// Sample route
app.get('/', (req, res) => {
    res.send('Hello World!');
});

// Error handling middleware
app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).send('Something broke!');
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

This sets up basic logging and error handling.

What if I want to log errors to a file instead of the console?

You can configure Winston to log errors to a file. Here's how:

const winston = require('winston');

const logger = winston.createLogger({
    level: 'error',
    format: winston.format.json(),
    transports: [
        new winston.transports.File({ filename: 'error.log' })
    ]
});

// In your error handling middleware
app.use((err, req, res, next) => {
    logger.error(err.stack);
    res.status(500).send('Something broke!');
});