How Should Unhandled Errors Preferably be Resolved in Node.js ?

Unhandled errors in Node.js can lead to unexpected application crashes, data corruption, and poor user experiences. Effectively managing these errors is crucial for building robust and reliable applications. In this article, we’ll explore best practices for handling unhandled errors in Node.js, ensuring your application remains stable and your users enjoy a seamless experience.

Understanding Unhandled Errors

Unhandled errors refer to exceptions or promise rejections that are not caught and managed by the application. These errors can occur for various reasons, such as bugs in the code, unexpected inputs, or failures in external services.

Types of Unhandled Errors in Node.js

• Uncaught Exceptions: Synchronous errors that occur outside of a try-catch block.
• Unhandled Promise Rejections: Rejections of promises that do not have a corresponding .catch handler.

Why Handling Unhandled Errors is Important

• Application Stability: Prevents crashes and keeps the application running smoothly.
• Data Integrity: Avoids potential data corruption caused by abrupt application terminations.
• User Experience: Ensures a consistent and reliable user experience without unexpected disruptions.
• Security: Prevents potential security vulnerabilities by ensuring errors are handled appropriately.

Resolving Unhandled Errors

To fix Node.js errors that aren’t being handled, you need to add error handling to your application. Most of the time, try-catch blocks, error handlers, and promise rejections are used in Node.js to handle errors. By putting in place ways to handle errors, you can catch and fix them before they cause your application to crash or do something else unexpected.

Steps to Setup Project for Unhandled Error

Step 1: Make a folder structure for the project.

mkdir myapp

Step 2: Navigate to the project directory

cd myapp

Step 3: Initialize the NodeJs project inside the myapp folder.

npm init -y

Step 4: Install the required npm packages using the following command.

npm install express

Project Structure:

The updated dependencies in package.json file will look like:

"dependencies": {
    "express": "^4.19.2",
  }

Using Try-catch Statements

Try-catch blocks are used to catch errors that happen at the same time as the program is running. The code that could throw an error is wrapped in a try-catch block. If there is an error, the catch block is run, and the error is caught and dealt with. Here’s what a try-catch block looks like:

Syntax:

try {
    // Code that can potentially throw an error
} catch (error) {
    // Error handling code
}

Note: However, be careful now, not to use try-catch in asynchronous code, as the error thrown by the async code will no longer be caught in the program.

Example: Implementation to show handling errors using try catch statememnt.

// app.js

function processData(data) {
  try {
    // Code that might throw an error
    let result = JSON.parse(data);
    console.log('Processed data:', result);
  } catch (error) {
    console.error('Error processing data:', error.message);
  }
}

processData('{"name": "Node.js"}'); // Correct JSON
processData('{name: "Node.js"}'); // Incorrect JSON

Output:

Using Error Handlers

Error handlers are used to catch errors that happen at different times during the runtime. In Node.js, you can make an error handler by implementing a middleware function that takes four arguments: err, req, res, and next. The error object is in the err argument, and the next argument is a function that passes control to the next middleware function. Here’s what an error handler looks like:

Example: Implementation to show handling errors using error handlers.

// app.js

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

// Example route that throws an error
app.get('/', (req, res, next) => {
  throw new Error('Something went wrong!');
});

// Centralized error handler
app.use((err, req, res, next) => {
  console.error('Error:', err.message);
  res.status(500).json({ error: err.message });
});

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

Output:

Using Promise Rejections

Errors in the promises may be found and corrected with the help of promise rejections. A call is made to the catch() function if a promise is broken; this allows any errors to be captured and dealt with appropriately. The following is an example of a broken promise:

Example: Implementation to show handling errors using promise rejections.

fetch('https://...com/data')
    .then(response => {
        // Process the response
    })
    .catch(error => {
        // Handle the error
    });

Most Effective Methods for Addressing Errors

You should adhere to these recommended practices if you want to manage unhandled failures with Node.js in an efficient manner:

• Any function that even remotely has the potential to generate an error, provides procedures for error handling.
• Make use of error messages that are detailed and give developers information that is helpful to them.
• To record mistakes in a database or log file, you may make use of a logging library.
• Error tracking in production settings may be accomplished with the help of error monitoring technologies such as Sentry, Rollbar, and Bugsnag.
• Do extensive testing on your methods for managing errors to validate that they perform as anticipated.

Conclusion

Handling unhandled errors in Node.js is crucial for building reliable and stable applications. By following these best practices, you can ensure that your application gracefully manages errors, preventing crashes and providing a consistent user experience. Always handle errors in asynchronous code, use centralized error handling, and log errors effectively to maintain the robustness of your Node.js applications.