NPM Scripts

npm Scripts and Package Management

Package.json Scripts

Common Script Patterns

{
  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "start": "node dist/index.js",
    "test": "vitest",
    "test:watch": "vitest watch",
    "test:coverage": "vitest --coverage",
    "lint": "eslint src/",
    "lint:fix": "eslint src/ --fix",
    "format": "prettier --write .",
    "format:check": "prettier --check .",
    "typecheck": "tsc --noEmit",
    "clean": "rm -rf dist node_modules/.cache",
    "prepare": "husky",
    "validate": "npm-run-all --parallel lint typecheck test:coverage"
  }
}

Pre/Post Hooks and Lifecycle Scripts

npm runs pre<script> before and post<script> after any script automatically:

{
  "scripts": {
    "prebuild": "npm run clean",
    "build": "tsc",
    "postbuild": "npm run copy-assets",
    "clean": "rm -rf dist",
    "copy-assets": "cp -r assets dist/",
    "prepare": "husky",
    "prepublishOnly": "npm run build && npm test",
    "postinstall": "patch-package"
  }
}

Built-in lifecycle scripts:

• prepare -- runs after npm install and before npm publish
• prepublishOnly -- runs before npm publish only (not on install)
• preinstall / postinstall -- before/after npm install
• prepack / postpack -- before/after tarball is created

Cross-Platform Scripts

{
  "devDependencies": {
    "cross-env": "^7.0.3",
    "shx": "^0.3.4",
    "npm-run-all2": "^6.0.0"
  },
  "scripts": {
    "build": "cross-env NODE_ENV=production webpack",
    "clean": "shx rm -rf dist",
    "dev": "run-p watch:css watch:js serve",
    "ci": "run-s lint typecheck test build",
    "lint:all": "run-p lint:js lint:css lint:html"
  }
}

• run-s -- sequential; run-p -- parallel
• Glob patterns: run-p lint:* runs all scripts matching lint:

Environment Variables

{
  "scripts": {
    "build:staging": "cross-env NODE_ENV=staging API_URL=https://staging.api.com vite build",
    "build:prod": "cross-env NODE_ENV=production vite build"
  }
}

npm exposes package.json fields as npm_package_* (e.g., npm_package_name, npm_package_version).

npx and bunx

npx create-next-app@latest my-app    # run without installing
npx -p typescript tsc --version      # specify package explicitly
npx vitest                           # run local binary from node_modules/.bin
bunx create-next-app@latest my-app   # Bun equivalent (faster)

Dependency Management

npm install                  # all deps from package.json
npm install lodash           # add production dep
npm install -D typescript    # dev dependency
npm install lodash@4.17.21   # exact version
npm install user/repo        # from GitHub
npm ci                       # clean install from lock file (CI)

npm outdated                 # list outdated packages
npm update                   # update within semver ranges
npx npm-check-updates -u     # update package.json beyond ranges
npm dedupe                   # remove duplicate packages
npm why lodash               # show why a package is installed
npm ls lodash                # find installed versions

npm audit                    # check vulnerabilities
npm audit fix                # auto-fix compatible vulnerabilities
npm audit --omit=dev         # audit production deps only

Overrides and Resolutions

Force a transitive dependency version:

{
  "overrides": { "glob": "^10.0.0" }
}

Yarn: "resolutions": { "glob": "^10.0.0" }. pnpm: "pnpm": { "overrides": { "glob": "^10.0.0" } }.

Lock Files

# ALWAYS commit lock files to version control
npm ci                        # deterministic install, fails if lock out of sync
npm ci --ignore-scripts       # skip lifecycle scripts
pnpm install --frozen-lockfile  # pnpm equivalent
yarn install --immutable       # yarn equivalent

Regenerate only when resolving deep conflicts or migrating package managers: delete node_modules and lock file, then npm install.

.npmrc Configuration

Project-level .npmrc (commit this):

save-exact=true
registry=https://registry.npmjs.org/
@mycompany:registry=https://npm.mycompany.com/
engine-strict=true

User-level ~/.npmrc (never commit):

//registry.npmjs.org/:_authToken=${NPM_TOKEN}
//npm.mycompany.com/:_authToken=${COMPANY_NPM_TOKEN}

Custom Registry Setup

Verdaccio (local/private)

npm install -g verdaccio && verdaccio
npm set registry http://localhost:4873/
npm publish --registry http://localhost:4873/

GitHub Packages

# .npmrc
@yourorg:registry=https://npm.pkg.github.com/
//npm.pkg.github.com/:_authToken=${GITHUB_TOKEN}

{ "publishConfig": { "registry": "https://npm.pkg.github.com/" } }

Workspaces (Monorepo)

Setup

{
  "name": "my-monorepo",
  "private": true,
  "workspaces": ["packages/*", "apps/*"]
}

Workspace Commands

npm install                              # install all (hoisted to root)
npm run build -w packages/shared         # run in specific workspace
npm run build -w @myorg/shared           # by package name
npm run test --workspaces                # run across all workspaces
npm run build -ws --if-present           # skip workspaces missing the script
npm install zod -w packages/shared       # add dep to workspace
npm install @myorg/shared -w apps/web    # add workspace as dependency

Monorepo Root Scripts

{
  "scripts": {
    "build": "npm run build --workspaces --if-present",
    "test": "npm run test --workspaces --if-present",
    "lint": "npm run lint --workspaces --if-present",
    "dev:web": "npm run dev -w apps/web",
    "dev:api": "npm run dev -w apps/api"
  }
}

npm hoists shared deps to root node_modules. Conflicts stay in the workspace's own node_modules. Use npm dedupe if duplication creeps in.

pnpm

pnpm install                   # install all
pnpm add lodash                # add dep
pnpm add -D typescript         # dev dep
pnpm dlx create-next-app       # like npx

# pnpm-workspace.yaml
packages:
  - 'packages/*'
  - 'apps/*'

pnpm -F web run build          # filter by name
pnpm -r run build              # all workspaces
pnpm -r --parallel run dev     # all in parallel
pnpm -F web... run build       # web and its dependencies

yarn

yarn add lodash                # add dep
yarn add -D typescript         # dev dep
yarn dev                       # run script (no 'run' needed)
yarn dlx create-next-app       # like npx (yarn berry)
yarn workspace web build       # workspace command
yarn workspaces foreach -A run build

Publishing

Package Setup

{
  "name": "@scope/package",
  "version": "1.0.0",
  "main": "dist/index.js",
  "module": "dist/index.mjs",
  "types": "dist/index.d.ts",
  "exports": {
    ".": {
      "import": "./dist/index.mjs",
      "require": "./dist/index.js",
      "types": "./dist/index.d.ts"
    }
  },
  "files": ["dist", "README.md", "LICENSE"],
  "publishConfig": { "access": "public" },
  "scripts": { "prepublishOnly": "npm run build && npm test" }
}

The files field whitelists what goes in the tarball. Prefer files over .npmignore.

Publish and Version

npm publish                     # publish to registry
npm publish --access public     # scoped packages (first time)
npm publish --dry-run           # preview what gets published
npm pack --dry-run              # list files that would be included
npm publish --provenance        # with build provenance (CI only)

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
npm version prerelease --preid=beta  # 1.0.0 -> 1.0.1-beta.0

npm version auto-updates package.json, creates a git commit, and tags it. Hook into the flow:

{
  "scripts": {
    "preversion": "npm test",
    "version": "npm run build && git add -A",
    "postversion": "git push && git push --tags && npm publish"
  }
}

Debugging Scripts

npm run build --verbose          # see exact command
npm run build --silent           # suppress npm output, show only script output
npm run                          # list all available scripts
node --inspect-brk dist/index.js # debugger, break on first line
NODE_OPTIONS='--inspect' npm run dev  # attach inspector to any script
DEBUG=express:* npm run dev      # debug logging (common pattern)
NODE_DEBUG=module node dist/index.js  # debug module resolution

Security

npm audit                        # check known vulnerabilities
npm audit --audit-level=high     # fail only on high/critical
npm audit signatures             # verify package signatures
npm ci                           # verifies lock file integrity checksums
npm publish --provenance         # build provenance (GitHub Actions)
npx @socketsecurity/cli report   # supply chain security report

Best practices:

• Run npm audit in CI pipelines
• Use npm ci (not npm install) in CI for reproducible builds
• Set save-exact=true in .npmrc for critical dependencies
• Use npm publish --provenance for public packages
• Never store auth tokens in committed .npmrc -- use environment variables

Quick Reference

npm init -y                    # create package.json
npm cache clean --force        # clear cache
npm config list                # show config
npm exec -- eslint .           # run local binary
npm link                       # symlink package for local dev
npm repo                       # open repo in browser
npm docs lodash                # open package docs
npm view lodash versions       # list published versions