Clean Code

Pragmatic refactoring patterns and coding standards. Not dogma — practical improvements.

Code Smells to Fix

Long functions (>30 lines)

Extract into named functions. The name documents intent better than a comment.

Deep nesting (>3 levels)

Use early returns, guard clauses, or extract helper functions.

// Bad
function process(user) {
  if (user) {
    if (user.active) {
      if (user.verified) {
        // actual logic
      }
    }
  }
}

// Good
function process(user) {
  if (!user) return;
  if (!user.active) return;
  if (!user.verified) return;
  // actual logic
}

Magic numbers/strings

Extract to named constants.

Duplicate code

If you copy-paste 3+ times, extract. Two occurrences are often fine.

Dead code

Delete it. Git has history if you need it back.

SOLID Principles (Practical Version)

• Single Responsibility — A function does one thing. A module handles one concern. If you can't name it simply, it does too much.
• Open/Closed — Extend with new code, don't modify working code. Use composition, interfaces, or strategy patterns.
• Liskov Substitution — Subtypes must work where parent types are expected. Don't override methods to throw "not implemented."
• Interface Segregation — Don't force clients to depend on methods they don't use. Smaller interfaces > fat interfaces.
• Dependency Inversion — Depend on abstractions, not concrete implementations. Pass dependencies in, don't create them inside.

Refactoring Techniques

Extract Function

# Find long functions
grep -rn "function\|=>\|def " src/ | awk -F: '{print $1}' | sort | uniq -c | sort -rn | head -10

Rename for clarity

# Find vague variable names
grep -rn "\bdata\b\|\btemp\b\|\bresult\b\|\binfo\b\|\bstuff\b" src/ --include="*.ts" --include="*.py" | head -20

Remove dead code

# Find unused exports (TypeScript)
npx ts-unused-exports tsconfig.json

# Find unused functions (crude)
grep -rn "function " src/ --include="*.ts" -l | while read f; do
  grep -oP "function \K\w+" "$f" | while read fn; do
    count=$(grep -rn "\b$fn\b" src/ --include="*.ts" | wc -l)
    [ "$count" -le 1 ] && echo "Possibly unused: $fn in $f"
  done
done

Simplify conditionals

Replace nested if/else with:

• Early returns
• Lookup tables/maps
• Polymorphism (if the condition is on type)

Naming Conventions

• Functions: verb + noun (getUser, validateEmail, parseResponse)
• Booleans: is/has/should prefix (isActive, hasPermission)
• Collections: plural (users, orderItems)
• Avoid: handle, process, manage without specificity — they say nothing

Notes

• Refactor in small, tested steps. Don't rewrite a whole file in one commit.
• Pragmatism over purity. Three similar lines are better than a premature abstraction.
• The best code needs no comments. But when logic isn't obvious, explain why, not what.
• Run tests after each refactoring step. If tests break, you changed behavior, not just structure.