Debugging and Logging

Debugging and logging are important parts of backend development. They help developers identify problems, track application behavior, and monitor requests inside an Express.js application.

One of the simplest debugging techniques is using console.log() to inspect values and request data.

Example:

app.get('/users', (req, res) => {
  console.log('Request received');

  res.send('Users route');
});

This can help you verify whether routes are being called correctly.

Logging Request Information

Logging is commonly used to track incoming requests, response times, and application errors.

Example:

app.use((req, res, next) => {
  console.log(`${req.method} ${req.url}`);

  next();
});

This middleware logs the HTTP method and requested URL for every request.

Example output:

GET /users
POST /users

Using Logging Libraries

In larger applications, developers usually use logging libraries instead of relying only on console.log().

A popular option in Express.js applications is Morgan.

Example:

const morgan = require('morgan');

app.use(morgan('dev'));

Morgan automatically logs request information in a cleaner and more structured format.

Debugging Errors

When debugging Express.js applications, developers often inspect:

• Route handlers;
• Middleware flow;
• Request parameters;
• Response status codes;
• Database operations.

Careful logging and structured debugging make applications easier to maintain and troubleshoot.