dry-refactoring

Guided workflow to eliminate copy-paste duplication in source code. Use after running jscpd to detect clones.

First, run jscpd to identify duplications:

npx jscpd --reporters ai <path>

In codebases that mix related formats (e.g. JavaScript and TypeScript), add --cross-formats so clones spanning both are detected too:

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

See the jscpd skill for full option reference, including cross-format group syntax.

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

Extract function — when the duplicate is a block of logic:

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

Extract module/utility — when the duplicate spans multiple files in different domains:

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

Extract constant or config — when the duplicate is repeated data or configuration.

Template/base class — when the duplicate is structural (e.g., repeated class shape).

Always ensure:

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

Score