How to Debug JavaScript Code Like a Pro | Expert Guide

Introduction

Debugging JavaScript can feel like solving a mystery. One minute your code works perfectly, and the next, it’s throwing errors you’ve never seen before. But don’t worry—every developer faces this challenge. In fact, a study found that developers spend up to 50% of their time debugging code. Want to cut that time in half? Sign up for our free JavaScript debugging course to sharpen your skills!

Let’s dive in and learn how to debug JavaScript like a pro.

Understanding JavaScript Errors

Types of JavaScript Errors

JavaScript errors tell you exactly where things went wrong. But to fix them, you need to understand what they mean.

Syntax Errors

These occur when the JavaScript engine encounters incorrect syntax.

• Example: console.log(“Hello World’ (missing closing quotation mark)

Runtime Errors

These happen during execution, such as calling undefined functions.

• Example: undefinedVariable(); // ReferenceError: undefinedVariable is not defined

Logical Errors

Your code runs but doesn’t produce the expected result.

• Example: if (score = 100) { console.log(“Win!”); } // Assignment instead of comparison

“The first step to debugging is accepting that you’ll make mistakes.” — Sarah Drasner, VP of Developer Experience at Netlify

Using console.log Like a Pro

console.log Best Practices

While console.log is helpful, excessive use can clutter your console. Instead:

• Use console.table for structured data (arrays, objects).
• Label your logs: console.log(‘User Data:’, userData);
• Measure execution time with console.time() and console.timeEnd().

Helpful Console Methods