Error Handling In JavaScript

Error handling in JavaScript is crucial for writing robust and reliable code. There are several mechanisms and best practices for handling errors effectively:

try...catch Statement: Used to handle exceptions (errors) that occur within a block of code. The syntax is as follows:

try {

// Code that may throw an error

} catch (error) {

// Code to handle the error

}

Here's an example:

try { let result = someFunctionThatMayThrowAnError(); console.log(result); } catch (error) { console.error('An error occurred:', error); }

throw Statement: Used to generate an exception manually. You can throw any JavaScript value (object, string, number, etc.):

function validateInput(input) { if (!input) { throw 'Input cannot be empty'; } // Other validation logic }

Error Object: JavaScript has built-in error types like Error, SyntaxError, ReferenceError, TypeError, etc. You can create custom error objects by extending the Error constructor:

class CustomError extends Error { constructor(message) { super(message); this.name = 'CustomError'; } } throw new CustomError('Something went wrong');

Global Error Handling: You can use the window.onerror event handler or window.addEventListener('error', handler) to capture unhandled errors globally:

window.onerror = function(message, source, lineno, colno, error) { console.error('Global error:', message, source, lineno, colno, error); };

Promises Error Handling: When working with Promises, you can use the .catch() method to handle errors:

fetch('https://api.example.com/data') .then(response => { if (!response.ok) { throw new Error('Network response was not ok'); } return response.json(); }) .then(data => console.log(data)) .catch(error => console.error('Fetch error:', error));

Async/Await Error Handling: When using async functions with the async and await keywords, you can use try...catch for error handling:

async function fetchData() { try { let response = await fetch('https://api.example.com/data'); let data = await response.json(); console.log(data); } catch (error) { console.error('Fetch error:', error); } }