dry-refactoring

Prerequisites

npx jscpd --reporters ai <path>

--cross-formats

npx jscpd --reporters ai --cross-formats "js-ts" <path>

Workflow

1. Run jscpd with

   --reporters ai

   on the target path
2. Parse each clone line to identify the two duplicated locations (file + line range)
3. Read both code fragments from the source files
4. Understand what the duplicated code does
5. Design a refactoring: extract a shared function, class, module, or constant
6. Apply the refactoring — update both locations and all other usages
7. Re-run jscpd to confirm the clone is eliminated
8. Repeat for remaining clones, highest-impact first

Refactoring Strategies

// Before: same block in two places
// After: shared function called from both places

// Move shared logic to a shared utility file and import it

• All call sites are updated, not just the two reported by jscpd
• Tests still pass after refactoring
• The extracted abstraction has a clear, descriptive name

Tips

• Start with clones that have the highest line count — they have the most impact
• A clone between test files may indicate a missing test helper
• Clones across unrelated modules may signal a missing shared utility
• A cross-format clone (same logic in a

  .js

  and a

  .ts

  file, found with

  --cross-formats

  ) often means code was ported without deleting the original — consolidate into one implementation (usually the TypeScript one) and update imports, rather than extracting a third shared copy
• Use

  --min-lines 10

  to filter noise and focus on meaningful duplications