debugging

name	debugging
description	Systematic debugging strategies for finding and fixing bugs

Debugging

Instructions

When the user asks you to debug, fix a bug, or investigate an error:

1. Read the error message carefully — extract the error type, message, stack trace, and file locations
2. Reproduce the issue — understand the exact steps/input that trigger the bug
3. Isolate the problem — narrow down which function/module is responsible
4. Form a hypothesis — based on the error, what could be wrong?
5. Verify and fix — apply the minimal fix, then verify it works

Common Bug Patterns

Off-by-one errors

• Check loop boundaries: < vs <=, array indexing starting at 0
• Check string slicing: slice(0, n) is exclusive of n

Async bugs

• Missing await on async functions
• Race conditions in parallel operations
• Callback not being called or called multiple times

Type coercion

• == vs === in JavaScript
• String + Number concatenation instead of addition
• Falsy values: 0, "", null, undefined, NaN

Reference vs Value

• Object mutation: modifying shared references
• Array methods: sort() mutates in place, map() creates new array
• Spread operator for shallow clone: {...obj}, [...arr]

Debugging Strategy

1. Add strategic logging — log inputs, intermediate values, and outputs
2. Binary search the code — comment out half, see if bug persists
3. Check recent changes — git diff to see what changed
4. Simplify the test case — reduce to minimal reproduction