Node.js and npm

Use Claude Code to automate npm package boilerplate generation, enforce TypeScript/linting configurations, and manage the entire publish workflow from testing to npm registry. Claude Code integrates with your development environment to generate package scaffolds, run tests, and handle versioning automatically. This guide shows you how to use these capabilities for faster, higher-quality package development.

Setting Up Your Development Environment

Before creating your first npm package with Claude Code, ensure your environment is properly configured.

Prerequisites

# Node.js and npm
node --version  # Should be v18 or higher
npm --version   # Should be v9 or higher

# Git configuration
git config --global user.name "Your Name"
git config --global user.email "your@email.com"

# Claude Code CLI
which claude  # Verify Claude Code is installed

Initialize Your Package Directory

mkdir my-npm-package && cd my-npm-package
npm init -y

Using Claude Code for Package Scaffolding

Claude Code can generate the entire package structure with proper configuration files.

Generate Basic Package Structure

claude "Create an npm package with ESM support, TypeScript types, Jest testing, ESLint, and Prettier. Include standard directories: src/, tests/, and dist/. Set up GitHub Actions CI workflow."

Claude Code creates:

package.json with proper metadata, scripts, and exports
TypeScript configuration (tsconfig.json)
Jest configuration for testing
ESLint and Prettier configurations
GitHub Actions workflow for CI/CD
Directory structure (src/, tests/)
Initial source files and test templates

Implementing Core Package Features

After scaffolding, implement your package functionality using Claude Code’s assistance.

Creating the Main Module

// src/index.ts
export interface PackageOptions {
  debug?: boolean;
  timeout?: number;
}

export class MyPackage {
  private debug: boolean;
  private timeout: number;

  constructor(options: PackageOptions = {}) {
    this.debug = options.debug ?? false;
    this.timeout = options.timeout ?? 5000;
  }

  async initialize(): Promise<void> {
    if (this.debug) {
      console.log('[MyPackage] Initializing...');
    }
  }

  async execute(data: string): Promise<string> {
    return data.toUpperCase();
  }
}

export default MyPackage;

Adding TypeScript Types

// src/types.ts
export interface PackageResult {
  success: boolean;
  data?: string;
  error?: Error;
}

export type PackageEvent =
  | { type: 'init'; timestamp: number }
  | { type: 'execute'; input: string; output: string }
  | { type: 'error'; error: Error };

Writing Tests with Claude Code

Claude Code helps generate test suites covering edge cases.

Generating Test Files

claude "Write Jest tests for the MyPackage class covering: constructor options, initialize method, execute method with various inputs, error handling, and edge cases like empty strings and null inputs."

Example Test Structure

// tests/MyPackage.test.ts
import { MyPackage } from '../src/index';

describe('MyPackage', () => {
  let pkg: MyPackage;

  beforeEach(() => {
    pkg = new MyPackage({ debug: true });
  });

  describe('constructor', () => {
    it('should use default options when not provided', () => {
      const defaultPkg = new MyPackage();
      expect(defaultPkg).toBeDefined();
    });

    it('should accept custom options', () => {
      const customPkg = new MyPackage({
        debug: true,
        timeout: 10000
      });
      expect(customPkg).toBeDefined();
    });
  });

  describe('execute', () => {
    it('should transform input to uppercase', async () => {
      const result = await pkg.execute('hello');
      expect(result).toBe('HELLO');
    });

    it('should handle empty strings', async () => {
      const result = await pkg.execute('');
      expect(result).toBe('');
    });
  });
});

Setting Up CI/CD Pipeline

Claude Code generates GitHub Actions workflows for automated testing and publishing.

CI Workflow Configuration

# .github/workflows/ci.yml
name: CI

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        node-version: [18.x, 20.x, 22.x]

    steps:
      - uses: actions/checkout@v4
      - name: Use Node.js ${{ matrix.node-version }}
        uses: actions/setup-node@v4
        with:
          node-version: ${{ matrix.node-version }}
          cache: 'npm'

      - run: npm ci
      - run: npm run lint
      - run: npm test
      - run: npm run build

Publishing Workflow

# .github/workflows/publish.yml
name: Publish

on:
  release:
    types: [created]

jobs:
  publish:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
          registry-url: 'https://registry.npmjs.org'

      - run: npm ci
      - run: npm test
      - run: npm run build
      - run: npm publish
        env:
          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}

Publishing Your Package

Follow these steps to publish your package to the npm registry.

Preparation Steps

# Update package.json with proper metadata
# - name: your-username/your-package
# - version: 1.0.0
# - description: Clear description
# - main: dist/index.js
# - types: dist/index.d.ts
# - repository: GitHub repo URL
# - keywords: relevant keywords

# Login to npm (one-time)
npm login

# Verify package name is available
npm view your-package-name

Publishing Commands

# Dry run to verify
npm publish --dry-run

# Publish to npm
npm publish

# Or publish with access level
npm publish --access public  # For scoped packages

Maintaining Your Package

Claude Code assists with ongoing maintenance tasks.

Version Management

# Update version semantically
npm version patch  # 1.0.0 -> 1.0.1
npm version minor  # 1.0.0 -> 1.1.0
npm version major  # 1.0.0 -> 2.0.0

Adding Features

claude "Add a new method to the package that implements caching with TTL support. Include tests and update TypeScript types."

Documentation Updates

claude "Generate API documentation from TypeScript types using TypeDoc. Include examples for each exported function and class."

Handling Backward Compatibility as Your Package Evolves

The hardest part of maintaining a public npm package is not building new features — it is removing or changing existing ones without breaking dependent projects. Claude Code helps you think through compatibility implications before making changes.

Before removing a deprecated method, add an explicit deprecation warning:

// src/deprecated.ts
export class MyPackage {
  /**
   * @deprecated Use `executeAsync` instead. Will be removed in v3.0.0.
   */
  execute(data: string): string {
    console.warn(
      '[MyPackage] execute() is deprecated. Use executeAsync() instead. ' +
      'This method will be removed in v3.0.0.'
    );
    return data.toUpperCase();
  }

  async executeAsync(data: string): Promise<string> {
    return data.toUpperCase();
  }
}

Run a deprecation cycle of at least two minor versions before removing anything. This gives downstream consumers two release cycles to migrate.

Use Claude Code to generate a migration guide whenever you make breaking changes:

claude "Review the diff between v1.x and v2.0 in this changelog. Generate a migration guide for users upgrading from v1 to v2, covering all breaking changes, renamed methods, and configuration changes."

The migration guide should live in MIGRATION.md at your package root and be linked from your README’s changelog section.

Publishing Dual Packages: ESM and CommonJS

Modern npm packages need to support both ES Modules (used by Vite, modern bundlers, and native Node.js ESM) and CommonJS (used by older Node.js projects and Jest). Configure your package.json exports field correctly:

{
  "name": "my-package",
  "version": "1.0.0",
  "main": "./dist/cjs/index.js",
  "module": "./dist/esm/index.js",
  "types": "./dist/types/index.d.ts",
  "exports": {
    ".": {
      "import": {
        "types": "./dist/types/index.d.ts",
        "default": "./dist/esm/index.js"
      },
      "require": {
        "types": "./dist/types/index.d.ts",
        "default": "./dist/cjs/index.js"
      }
    }
  }
}

Configure TypeScript to output both formats:

// tsconfig.esm.json
{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "module": "ESNext",
    "outDir": "./dist/esm"
  }
}

# Build script in package.json
"build": "tsc -p tsconfig.esm.json && tsc -p tsconfig.cjs.json && tsc --emitDeclarationOnly -p tsconfig.types.json"

Ask Claude Code to audit your package.json exports field and verify that bundler tools resolve both formats correctly. Edge cases in the exports field — especially around subpath exports and conditional exports — are a common source of “works in my project, breaks in yours” reports.

Automating Package Quality with Claude Code

Beyond test generation, Claude Code can perform ongoing quality checks as part of your development workflow.

API surface review: Before each release, ask Claude Code to review your public API for consistency:

claude "Review the exported types in src/index.ts. Flag: method naming inconsistencies, parameter ordering that doesn't follow a clear convention, missing JSDoc on public methods, and any methods that could cause confusion with similar-sounding built-in JavaScript methods."

Bundle size analysis: Large bundle sizes hurt downstream consumers. Use size-limit to enforce bundle budgets:

npm install --save-dev size-limit @size-limit/preset-small-lib

// package.json
"size-limit": [
  {
    "path": "dist/esm/index.js",
    "limit": "10 KB"
  }
]

Ask Claude Code to suggest size optimizations when the bundle exceeds your target:

claude "The bundle size for this npm package exceeds our 10KB limit. Review the imports in src/index.ts and suggest which dependencies could be made optional or replaced with lighter alternatives."

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