Error Handling in Express JS

Express JS is a popular web application framework for Node.js that provides a robust set of features for building web applications. One important aspect of building any application is error handling. In this article, we will discuss how to handle errors in an Express JS application.

Middleware Error Handling

In Express JS, you can use middleware to handle errors. Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. You can create custom error-handling middleware functions and use them to catch errors and handle them appropriately.

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

Error Handling in Route Handlers

You can also handle errors in route handlers by using the try-catch block. This allows you to catch errors that occur within the route handler and handle them accordingly.

app.get('/example', async (req, res) => {
  try {
    // code that may throw an error
  } catch (err) {
    console.error(err);
    res.status(500).send('An error occurred');
  }
});
    

Error Handling in Asynchronous Code

When working with asynchronous code in Express JS, it is important to handle errors that may occur. You can use the try-catch block or the .catch() method on promises to catch errors and handle them appropriately.

app.get('/example', (req, res) => {
  someAsyncFunction().then(() => {
    // do something
  }).catch(err => {
    console.error(err);
    res.status(500).send('An error occurred');
  });
});
    

Conclusion

Error handling is an important aspect of building any application, and Express JS provides various mechanisms for handling errors in a Node.js web application. By using middleware, try-catch blocks, and proper error handling techniques, you can ensure that your application is robust and able to handle errors gracefully.