Debugging is the process of identifying and fixing errors in a program.
Debugging is finding and fixing errors in code. Every developer spends significant time debugging - code rarely works perfectly the first time.
Good debugging separates junior developers from experienced ones. Juniors guess randomly. Experienced developers debug systematically.
Syntax Errors: Typos, missing brackets, incorrect syntax. Your editor usually catches these.
Logic Errors: Code runs but produces wrong results. These are trickier - the code works, just not how you intended.
Runtime Errors: Code crashes while running. Null references, division by zero, file not found.
Console Logging: The simplest method. Add console.log() to see what values are at different points.
console.log("User data:", user);
console.log("Before API call");
Works everywhere, requires no setup.
Breakpoints: Pause code execution at specific lines. Inspect variables, step through code line by line. Use browser DevTools or IDE debuggers.
Rubber Duck Debugging: Explain your code out loud (even to a rubber duck). Often you spot the bug while explaining.
Discover why each component needs crystal-clear, non-overlapping responsibilities.
How to Evaluate a Good System Design Binary Search: Bug is somewhere in 100 lines? Comment out half. Still broken? Bug is in the remaining half. Repeat until found.
Browser DevTools: Console shows errors, debugger lets you step through code, network tab shows API failures.
IDE Debuggers: VS Code, WebStorm have built-in debuggers. Set breakpoints, inspect variables, watch expressions.
Error Tracking: Sentry, Rollbar catch production errors and show stack traces. Know when users hit bugs before they report them.
Your form submission fails silently. No error message, nothing happens.
Do not guess randomly. Form a hypothesis, test it, learn from the result.
Reproduce consistently. If you cannot make the bug happen reliably, you cannot fix it.
Simplify. Strip away code until you find the minimum that reproduces the bug.
Read error messages. They usually tell you exactly what is wrong and where.
Changing multiple things at once: You fix the bug but do not know which change did it.
Not reading errors carefully: The error message often contains the answer.
Giving up too quickly: Debugging is detective work. Persistence matters.
You will spend 30-50% of development time debugging. Getting good at it makes you dramatically more productive. The faster you find and fix bugs, the faster you ship features.
Senior developers are not necessarily better at writing bug-free code - they are better at finding and fixing bugs quickly when they inevitably appear.
