refactor-clean

Refactor & Clean Code

When to Use

• Code is correct but hard to read, modify, or extend
• Duplicated logic exists across multiple files
• Functions or classes have grown too large
• Preparing code for a new feature that requires structural changes
• After a rapid prototype that needs production-quality cleanup

Prerequisites

• Existing tests that cover the code to refactor (add tests first if missing)
• All tests passing before starting
• Code committed so you can revert if needed

Workflow

1. Identify Code Smells

# Find long files (likely doing too much)
Get-ChildItem -Recurse -Include *.ts,*.js,*.py,*.go | Where-Object { (Get-Content $_.FullName | Measure-Object -Line).Lines -gt 300 } | Select-Object FullName, @{N='Lines';E={(Get-Content $_.FullName | Measure-Object -Line).Lines}}

# Find duplicated string patterns
grep -rn "pattern-you-suspect-is-duplicated" src/ --include="*.ts"

# Find functions with too many parameters (>4 is a smell)
grep -n "function.*,.*,.*,.*," src/**/*.ts

Common smells to look for:

• Long functions (>40 lines) — extract smaller functions
• Duplicate code — extract shared utility
• Deep nesting (>3 levels) — use early returns or extract
• God objects — split into focused classes/modules
• Primitive obsession — introduce domain types
• Feature envy — move logic to the class that owns the data

2. Establish a Safety Net

# Run existing tests and record baseline
npm test 2>&1 | Tee-Object -Variable baseline
echo $baseline | Select-Object -Last 5

# If coverage is low, write characterization tests first
npm test -- --coverage --collectCoverageFrom="src/module-to-refactor.ts"

3. Plan the Refactoring

Before touching code, decide on the transformation:

• Extract Function — pull a block into a named function
• Extract Module — move related functions to a new file
• Rename — improve names for clarity
• Inline — remove unnecessary indirection
• Replace Conditional with Polymorphism — use strategy pattern
• Introduce Parameter Object — group related parameters