버그 범위 좁히기
인공지능의 도움으로 문제를 격리하십시오.
버그 범위 좁히기은(는) CoddyKit의 무료 Vibe Coding 강의입니다. 이것은 4개 중 3번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Vibe Coding 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Vibe Coding 강의에는 총 4개의 강의가 포함되어 있습니다.
이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.
When There's No Clear Error
Sometimes nothing crashes — the app just does the wrong thing. The button doesn't work, the total is wrong, the data never shows up. No red text to paste.
This is where real debugging begins: narrowing down where the problem actually lives. The good news? AI is an incredible partner for this — if you know how to drive the investigation.
The Core Idea: Divide and Conquer
A bug hides somewhere between your input and your output. Your job is to cut the search space in half, over and over, until you've cornered it.
Think of it like finding a broken light in a string of bulbs: you check the middle first. Is the first half fine? Then the break is in the second half. This is the single most powerful debugging mindset there is.
Your Best Friend: console.log
The simplest tool to narrow a bug is printing values at different points. Run this — the logs show you exactly what each variable holds along the way.
When the printed value isn't what you expected, you've found the rough location of the bug.
function getDiscountedPrice(price, percent) {
console.log("input price:", price);
console.log("input percent:", percent);
const discount = price * percent;
console.log("discount:", discount);
return price - discount;
}
console.log("final:", getDiscountedPrice(100, 20));Read the Trail
Look at the output you just saw. The final price came out negative! The logs reveal why: percent was 20, but the math expected 0.20. The discount log showed 2000 — an obvious giveaway.
That's narrowing in action: the logs pointed at the exact line where reality diverged from your expectation. You don't fix blindly — you locate, then fix.
Ask AI to Add the Logs
You don't have to place logs by hand. Ask your AI tool to instrument the code for you. This is a perfect job for Cursor, Claude Code, or Copilot.
"This function returns the wrong total and I can't tell
why. Add console.log statements at each step so I can
see how the value changes. Don't change the logic yet —
just help me see what's happening."Comment Out to Isolate
Another narrowing trick: temporarily disable chunks of code. If you suspect a section, comment it out (or return early) and see if the problem disappears.
If the bug goes away, it lives in the part you removed. If it stays, look elsewhere. You're shrinking the haystack with every test.
function renderPage() {
loadHeader();
// loadSidebar(); // <- commented out to test
loadContent();
}
// Bug gone? The problem was in loadSidebar().
// Bug still here? Look at loadHeader or loadContent.Check Your Assumptions
Most stubborn bugs come from a wrong assumption: 'I assumed this variable held a number, but it's actually text.' Narrowing means testing those assumptions one by one.
A great AI prompt for this:
"Here's my function and what I expect each variable to
hold. Tell me which of my assumptions might be wrong,
and suggest one console.log I could add to confirm
the most likely one."Type Confusion Is Sneaky
A super common hidden bug: a value is text when you think it's a number. Run this — the result looks crazy until you realize "5" is a string, so + glues instead of adds.
Logging the type (not just the value) instantly reveals these.
const quantity = "5"; // came from a form input as text
const price = 10;
console.log("sum looks like:", quantity + price);
console.log("type of quantity:", typeof quantity);
console.log("fixed:", Number(quantity) + price);Narrow the Steps to Reproduce
Narrowing isn't only about code — it's about actions. Find the smallest sequence that triggers the bug.
Does it happen every time, or only with an empty field? Only on the second click? Only with certain data? Each answer shrinks the suspect list. Hand these findings to AI:
"I narrowed it down: the crash only happens when the
search box is EMPTY and I press Enter. With any text
it works fine. Given this, where should I look in
this handler function? [paste function]"Use the Debugger for Hard Cases
For trickier bugs, browser DevTools and editors like Cursor let you set a breakpoint — the code pauses on a line so you can inspect every variable at that moment.
You don't need it for everything; console.log handles most cases. But know it exists. You can even ask AI: 'Where should I put a breakpoint to catch this?' and it'll point you to the right line.
A Narrowing Workflow
Put it together into a repeatable loop:
- 1. Describe expected vs actual output
- 2. Log or disable a midpoint to split the problem in half
- 3. Check which half the bug is in
- 4. Repeat until you've cornered the exact line
- 5. Hand AI the narrowed location + your findings for a precise fix
This turns 'somewhere in my 500 lines' into 'this one line on line 42'.
Quick Check
Your app shows a wrong total but throws no error. What's the smartest first move to narrow it down?
Recap: You Can Corner Any Bug
You learned to debug even when there's no error to paste. Your toolkit now includes:
- Divide and conquer — cut the search space in half repeatedly
- console.log values and types to see reality
- Comment out sections to isolate the culprit
- Test your assumptions and minimize the steps to reproduce
- Let AI add logs, suggest breakpoints, and confirm assumptions
But what if you and the AI both get stuck in a loop? That's the final lesson: when AI gets stuck.
자주 묻는 질문
“버그 범위 좁히기” 강의는 무료인가요?
네 — “버그 범위 좁히기” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 Vibe Coding 강의 전체를 잠금 해제할 수 있습니다. Vibe Coding 강의에는 총 4개의 강의가 포함되어 있습니다.
“버그 범위 좁히기”에서 뭘 배우나요?
인공지능의 도움으로 문제를 격리하십시오. 브라우저에서 직접 실행하는 실습 코드로 Vibe Coding을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.
Vibe Coding을(를) 시작하는 데 경험이 필요한가요?
사전 경험은 필요하지 않습니다. CoddyKit의 Vibe Coding은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 4개 중 3번째 강의입니다.
“버그 범위 좁히기” 강의는 얼마나 걸리나요?
대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.
이 Vibe Coding 강의에서 코드를 작성하고 실행할 수 있나요?
네. 모든 Vibe Coding 강의에는 내장 코드 에디터가 포함되어 있으므로, 브라우저에서 바로 실제 코드를 작성하고 실행한 후 즉시 AI 피드백을 받을 수 있습니다 — 로컬 설정이 필요 없습니다.