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package-json-scaffolder skill

/package-json-scaffolder

This skill generates complete, production-ready package.json files with sensible defaults and current LTS dependencies for Node.js projects.

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---
name: package-json-scaffolder
description: Generate complete package.json files with appropriate dependencies, scripts, and configuration for Node.js projects of various types. Triggers on "create package.json", "generate package.json for", "npm init for", "node project setup".
---

# Package.json Scaffolder

Generate complete, production-ready `package.json` files with appropriate dependencies, scripts, and metadata for various Node.js project types.

## Output Requirements

**File Output:** `package.json`
**Format:** Valid JSON with 2-space indentation
**Compatibility:** npm, yarn, pnpm compatible

## When Invoked

Immediately generate a complete `package.json` with sensible defaults. Use current LTS versions for dependencies unless specified otherwise.

## JSON Structure

### Required Fields
```json
{
  "name": "project-name",
  "version": "1.0.0",
  "description": "Project description",
  "main": "index.js",
  "scripts": {},
  "dependencies": {},
  "devDependencies": {}
}
```

### Recommended Fields
```json
{
  "author": "Author Name <[email protected]>",
  "license": "MIT",
  "repository": {
    "type": "git",
    "url": "https://github.com/user/repo.git"
  },
  "keywords": ["keyword1", "keyword2"],
  "engines": {
    "node": ">=18.0.0"
  }
}
```

## Project Type Templates

### React Application (Vite)
```json
{
  "name": "react-app",
  "private": true,
  "version": "0.0.0",
  "type": "module",
  "scripts": {
    "dev": "vite",
    "build": "tsc && vite build",
    "lint": "eslint . --ext ts,tsx --report-unused-disable-directives --max-warnings 0",
    "preview": "vite preview",
    "test": "vitest",
    "test:coverage": "vitest run --coverage"
  },
  "dependencies": {
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "react-router-dom": "^6.22.0"
  },
  "devDependencies": {
    "@types/react": "^18.2.55",
    "@types/react-dom": "^18.2.19",
    "@typescript-eslint/eslint-plugin": "^7.0.0",
    "@typescript-eslint/parser": "^7.0.0",
    "@vitejs/plugin-react": "^4.2.1",
    "eslint": "^8.56.0",
    "eslint-plugin-react-hooks": "^4.6.0",
    "eslint-plugin-react-refresh": "^0.4.5",
    "typescript": "^5.3.3",
    "vite": "^5.1.0",
    "vitest": "^1.2.0",
    "@vitest/coverage-v8": "^1.2.0"
  }
}
```

### Next.js Application
```json
{
  "name": "nextjs-app",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "dev": "next dev",
    "build": "next build",
    "start": "next start",
    "lint": "next lint",
    "test": "jest",
    "test:watch": "jest --watch"
  },
  "dependencies": {
    "next": "14.1.0",
    "react": "^18.2.0",
    "react-dom": "^18.2.0"
  },
  "devDependencies": {
    "@types/node": "^20.11.0",
    "@types/react": "^18.2.55",
    "@types/react-dom": "^18.2.19",
    "eslint": "^8.56.0",
    "eslint-config-next": "14.1.0",
    "typescript": "^5.3.3",
    "jest": "^29.7.0",
    "@types/jest": "^29.5.12",
    "jest-environment-jsdom": "^29.7.0"
  }
}
```

### Express API Server
```json
{
  "name": "express-api",
  "version": "1.0.0",
  "description": "Express REST API",
  "main": "dist/index.js",
  "scripts": {
    "dev": "tsx watch src/index.ts",
    "build": "tsc",
    "start": "node dist/index.js",
    "lint": "eslint src --ext .ts",
    "test": "jest",
    "test:watch": "jest --watch",
    "db:migrate": "prisma migrate dev",
    "db:generate": "prisma generate"
  },
  "dependencies": {
    "express": "^4.18.2",
    "cors": "^2.8.5",
    "helmet": "^7.1.0",
    "morgan": "^1.10.0",
    "dotenv": "^16.4.1",
    "zod": "^3.22.4",
    "@prisma/client": "^5.9.0"
  },
  "devDependencies": {
    "@types/express": "^4.17.21",
    "@types/cors": "^2.8.17",
    "@types/morgan": "^1.9.9",
    "@types/node": "^20.11.0",
    "typescript": "^5.3.3",
    "tsx": "^4.7.0",
    "prisma": "^5.9.0",
    "eslint": "^8.56.0",
    "@typescript-eslint/eslint-plugin": "^7.0.0",
    "@typescript-eslint/parser": "^7.0.0",
    "jest": "^29.7.0",
    "@types/jest": "^29.5.12",
    "ts-jest": "^29.1.2"
  },
  "engines": {
    "node": ">=18.0.0"
  }
}
```

### CLI Tool
```json
{
  "name": "my-cli-tool",
  "version": "1.0.0",
  "description": "A command-line tool",
  "bin": {
    "mycli": "./dist/cli.js"
  },
  "main": "dist/index.js",
  "types": "dist/index.d.ts",
  "files": [
    "dist"
  ],
  "scripts": {
    "dev": "tsx src/cli.ts",
    "build": "tsup src/index.ts src/cli.ts --format cjs,esm --dts",
    "lint": "eslint src --ext .ts",
    "test": "vitest",
    "prepublishOnly": "npm run build"
  },
  "dependencies": {
    "commander": "^12.0.0",
    "chalk": "^5.3.0",
    "ora": "^8.0.1",
    "inquirer": "^9.2.14"
  },
  "devDependencies": {
    "@types/node": "^20.11.0",
    "@types/inquirer": "^9.0.7",
    "typescript": "^5.3.3",
    "tsx": "^4.7.0",
    "tsup": "^8.0.1",
    "eslint": "^8.56.0",
    "@typescript-eslint/eslint-plugin": "^7.0.0",
    "@typescript-eslint/parser": "^7.0.0",
    "vitest": "^1.2.0"
  },
  "engines": {
    "node": ">=18.0.0"
  },
  "keywords": ["cli", "tool"]
}
```

### NPM Library Package
```json
{
  "name": "@scope/my-library",
  "version": "1.0.0",
  "description": "A reusable library",
  "main": "dist/index.js",
  "module": "dist/index.mjs",
  "types": "dist/index.d.ts",
  "exports": {
    ".": {
      "require": "./dist/index.js",
      "import": "./dist/index.mjs",
      "types": "./dist/index.d.ts"
    }
  },
  "files": [
    "dist"
  ],
  "scripts": {
    "build": "tsup src/index.ts --format cjs,esm --dts --clean",
    "dev": "tsup src/index.ts --format cjs,esm --dts --watch",
    "lint": "eslint src --ext .ts",
    "test": "vitest",
    "test:coverage": "vitest run --coverage",
    "prepublishOnly": "npm run lint && npm run test && npm run build"
  },
  "dependencies": {},
  "devDependencies": {
    "typescript": "^5.3.3",
    "tsup": "^8.0.1",
    "eslint": "^8.56.0",
    "@typescript-eslint/eslint-plugin": "^7.0.0",
    "@typescript-eslint/parser": "^7.0.0",
    "vitest": "^1.2.0",
    "@vitest/coverage-v8": "^1.2.0"
  },
  "peerDependencies": {},
  "engines": {
    "node": ">=18.0.0"
  },
  "publishConfig": {
    "access": "public"
  },
  "keywords": [],
  "repository": {
    "type": "git",
    "url": "https://github.com/user/repo.git"
  },
  "license": "MIT"
}
```

### Monorepo Root (Turborepo)
```json
{
  "name": "monorepo",
  "private": true,
  "workspaces": [
    "apps/*",
    "packages/*"
  ],
  "scripts": {
    "build": "turbo run build",
    "dev": "turbo run dev",
    "lint": "turbo run lint",
    "test": "turbo run test",
    "format": "prettier --write \"**/*.{ts,tsx,md}\""
  },
  "devDependencies": {
    "turbo": "^1.12.0",
    "prettier": "^3.2.4",
    "eslint": "^8.56.0"
  },
  "packageManager": "[email protected]",
  "engines": {
    "node": ">=18.0.0"
  }
}
```

## Common Script Patterns

### Development
```json
{
  "dev": "tsx watch src/index.ts",
  "dev:debug": "tsx watch --inspect src/index.ts"
}
```

### Building
```json
{
  "build": "tsc",
  "build:watch": "tsc --watch",
  "clean": "rm -rf dist"
}
```

### Testing
```json
{
  "test": "vitest",
  "test:watch": "vitest --watch",
  "test:coverage": "vitest run --coverage",
  "test:e2e": "playwright test"
}
```

### Linting & Formatting
```json
{
  "lint": "eslint . --ext .ts,.tsx",
  "lint:fix": "eslint . --ext .ts,.tsx --fix",
  "format": "prettier --write .",
  "format:check": "prettier --check ."
}
```

### Database
```json
{
  "db:migrate": "prisma migrate dev",
  "db:push": "prisma db push",
  "db:generate": "prisma generate",
  "db:studio": "prisma studio",
  "db:seed": "tsx prisma/seed.ts"
}
```

## Validation Checklist

Before outputting, verify:
- [ ] Valid JSON syntax
- [ ] 2-space indentation
- [ ] Name is lowercase, no spaces (use hyphens)
- [ ] Version follows semver (x.y.z)
- [ ] Scripts are appropriate for project type
- [ ] Dependencies use `^` for minor version flexibility
- [ ] DevDependencies vs dependencies are correct
- [ ] Engine requirements specified if needed
- [ ] No duplicate dependencies

## Example Invocations

**Prompt:** "Create package.json for a React TypeScript project with testing"
**Output:** Complete `package.json` with Vite, React, TypeScript, Vitest configured.

**Prompt:** "Generate package.json for Express API with Prisma"
**Output:** Complete `package.json` with Express, Prisma, testing scripts.

**Prompt:** "Package.json for publishable npm library"
**Output:** Complete `package.json` with proper exports, types, and publish config.

Overview

This skill generates complete, production-ready package.json files tailored to different Node.js project types. It outputs valid, nicely formatted JSON with sensible defaults, appropriate dependencies, scripts, and engine constraints. Use it to quickly scaffold package.json for apps, libraries, CLIs, APIs, and monorepos.

How this skill works

When triggered it inspects the requested project type and purpose, then composes a package.json with required fields (name, version, main, scripts, dependencies, devDependencies) and recommended metadata (author, license, repository, engines). It chooses current LTS-compatible versions, groups packages into dependencies vs devDependencies, and applies common script patterns for development, build, test, lint, and database tasks. Final output is validated for JSON syntax, semver, name formatting, and common mistakes before returning.

When to use it

  • Scaffolding a new React, Next.js, or Vite app
  • Bootstrapping an Express API with TypeScript and Prisma
  • Preparing a publishable npm library with exports and types
  • Creating CLI tools with proper bin / build scripts
  • Initializing a monorepo root with workspaces and turbo scripts

Best practices

  • Use lowercase, hyphen-separated project names and semver x.y.z for version
  • Put runtime libraries in dependencies and build/test tooling in devDependencies
  • Include engines.node when targeting specific Node LTS versions
  • Provide scripts for dev, build, lint, test, and a clean/build pipeline
  • Add repository, license, and keywords to improve discoverability and package metadata

Example use cases

  • Create package.json for a React TypeScript app with Vite, TypeScript, Vitest, and ESLint
  • Generate package.json for an Express REST API using TypeScript, Prisma, and Jest
  • Scaffold package.json for a publishable npm library with CJS+ESM exports, types, and prepublish checks
  • Build package.json for a CLI tool with bin entry, tsup build, and dev tooling
  • Initialize monorepo root package.json with pnpm/pnpm-workspaces or Turbo repo scripts

FAQ

Can you target a specific Node version?

Yes — specify engines.node and the scaffold will set the requested minimum Node version (recommended >=18 for modern toolchains).

Do dependencies use exact versions or ranges?

Dependencies are generated with caret ranges (e.g. ^5.3.3) to allow safe minor/patch upgrades by default.