Error Handling in Node.js

Introduction

Error handling is a crucial aspect of building robust applications in Node.js. This lesson will cover various error types, handling techniques, and best practices for error management.

Types of Errors

• Syntax Errors: Errors in the syntax of the code.
• Runtime Errors: Errors that occur during the execution of the program.
• Logical Errors: Errors that produce incorrect results but do not crash the program.
• Asynchronous Errors: Errors that occur in asynchronous operations.

Using Try-Catch

The try...catch statement is a common way to handle errors in synchronous code.

try {
    // Code that may throw an error
    const result = riskyFunction();
} catch (error) {
    console.error('An error occurred:', error.message);
}
            

Error Event

In Node.js, many core modules emit an 'error' event. This event must be handled to prevent the application from crashing.

const EventEmitter = require('events');
const myEmitter = new EventEmitter();

myEmitter.on('error', (err) => {
    console.error('An error occurred:', err.message);
});

// Emit an error
myEmitter.emit('error', new Error('Something went wrong!'));
            

Promise Error Handling

When using promises, handle errors with .catch() or use async/await with try-catch.

async function asyncFunction() {
    try {
        const data = await fetchData();
    } catch (error) {
        console.error('Error fetching data:', error.message);
    }
}

// Using .catch()
fetchData()
    .then(data => console.log(data))
    .catch(error => console.error('Error fetching data:', error.message));
            

Best Practices

• Always handle errors: Use try-catch and promise error handling.
• Log errors for debugging: Use a logging library for structured logging.
• Graceful degradation: Ensure the application can continue running in case of an error.
• Provide meaningful feedback: Inform users of errors without exposing sensitive information.

FAQ