jscpd

Copy/paste detector for programming source code, supports 150+ formats.

Copy/paste is a common technical debt on a lot of projects. The jscpd gives the ability to find duplicated blocks implemented on more than 150 programming languages and digital formats of documents.
The jscpd tool implements Rabin-Karp algorithm for searching duplications.

Packages of jscpd

name	version	description
jscpd		main package for jscpd (cli and API for detections included)
jscpd-server		jscpd server application
@jscpd/core		core detection algorithm, can be used for detect duplication in different environments, one dependency to eventemitter3
@jscpd/finder		detector of duplication in files
@jscpd/tokenizer		tool for tokenize programming source code
@jscpd/leveldb-store		LevelDB store, used for big repositories, slower than default store
@jscpd/html-reporter		Html reporter for jscpd
@jscpd/badge-reporter		Badge reporter for jscpd

AI Agent Skill

jscpd includes an agent skill for detecting and eliminating code duplication with AI coding assistants (Claude, Copilot, Gemini, Cursor, etc.).

npx skills add kucherenko/jscpd

Once installed, the skill teaches your agent to run jscpd with the ai reporter and refactor detected duplications.

Installation

$ npm install -g jscpd

Usage

$ npx jscpd /path/to/source

or

$ jscpd /path/to/code

or

$ jscpd --pattern "src/**/*.js"

More information about cli here.

JSCPD Server

JSCPD Server is a standalone application that provides an API for detecting code duplication. It can be used to integrate duplication detection into your services or tools.

Installation

$ npm install -g jscpd-server

Usage

Start the server:

$ jscpd-server

Check code for duplication:

$ curl -X POST http://localhost:3000/api/check \
  -H "Content-Type: application/json" \
  -d '{
    "code": "console.log(\"hello\");\nconsole.log(\"world\");",
    "format": "javascript"
  }'

More information about server here.

Programming API

For integration copy/paste detection to your application you can use programming API:

jscpd Promise API

import {IClone} from '@jscpd/core';
import {jscpd} from 'jscpd';

const clones: Promise<IClone[]> = jscpd(process.argv);

jscpd async/await API

import {IClone} from '@jscpd/core';
import {jscpd} from 'jscpd';
(async () => {
  const clones: IClone[] = await jscpd(['', '', __dirname + '/../fixtures', '-m', 'weak', '--silent']);
  console.log(clones);
})();

detectClones API

import {detectClones} from "jscpd";

(async () => {
  const clones = await detectClones({
    path: [
      __dirname + '/../fixtures'
    ],
    silent: true
  });
  console.log(clones);
})()

detectClones with persist store

import {detectClones} from "jscpd";
import {IMapFrame, MemoryStore} from "@jscpd/core";

(async () => {
  const store = new MemoryStore<IMapFrame>();

  await detectClones({
    path: [
      __dirname + '/../fixtures'
    ],
  }, store);

  await detectClones({
    path: [
      __dirname + '/../fixtures'
    ],
    silent: true
  }, store);
})()

In case of deep customisation of detection process you can build your own tool with @jscpd/core, @jscpd/finder and @jscpd/tokenizer.

Start contribution

• Fork the repo kucherenko/jscpd
• Clone forked version (git clone https://github.com/{your-id}/jscpd)
• Install dependencies (pnpm install)
• Run the project in dev mode: pnpm dev (watch changes and rebuild the packages)
• Add your changes
• Add tests and check it with pnpm test
• Build your project pnpm build
• Create PR

Who uses jscpd

• GitHub Super Linter is combination of multiple linters to install as a GitHub Action
• Code-Inspector is a code analysis and technical debt management service.
• Mega-Linter is a 100% open-source linters aggregator for CI (GitHub Action & other CI tools) or to run locally
• Codacy automatically analyzes your source code and identifies issues as you go, helping you develop software more efficiently with fewer issues down the line.
• Natural is a general natural language facility for nodejs. It offers a broad range of functionalities for natural language processing.

Backers

Thank you to all our backers! 🙏 [Become a backer]

Sponsors

Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [Become a sponsor]

License

MIT © Andrey Kucherenko