Cómo acotar un error
Aísle el problema con ayuda de la IA
Cómo acotar un error es una lección gratuita de Vibe Coding en CoddyKit. Esta es la lección 3 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de Vibe Coding, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de Vibe Coding incluye 4 lecciones en total.
Partes de esta lección aún no han sido traducidas y se muestran en inglés.
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.
Aprende JavaScript con un tutor de IA — gratis
Escribe y ejecuta código real en tu navegador, obtén ayuda instantánea de un tutor de IA disponible 24/7 y continúa donde lo dejaste en la web o en la aplicación.
- Cursos
- 25
- Lecciones
- 100
Preguntas frecuentes
¿La lección «Cómo acotar un error» es gratis?
Sí — el texto completo de «Cómo acotar un error» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de Vibe Coding, actualiza a CoddyKit PRO. El curso de Vibe Coding incluye 4 lecciones en total.
¿Qué aprenderé en «Cómo acotar un error»?
Aísle el problema con ayuda de la IA Practicas Vibe Coding con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.
¿Necesito experiencia previa para empezar Vibe Coding?
No se requiere experiencia previa. Vibe Coding en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 3 de 4.
¿Cuánto tiempo toma la lección «Cómo acotar un error»?
La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.
¿Puedo escribir y ejecutar código en esta lección de Vibe Coding?
Sí. Cada lección de Vibe Coding incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.
Todas las lecciones de este curso
- Cómo entender los mensajes de error
- Cómo pegar errores en la IA eficazmente
- Cómo acotar un error
- Cuando la IA se atasca