Modules, Runtime & Tooling

Package Managers, Lockfiles & Scripts

Package managers install dependency graphs, run scripts, maintain lockfiles, and shape reproducible builds. npm, pnpm, Yarn, and Bun differ in details, but the core concerns are dependency boundaries and repeatability.

A package manifest declares intent
A lockfile records resolution
Dependency categories matter
Scripts are project API
pnpm-style strictness exposes hidden dependency assumptions

Useful package scripts

{
  "scripts": {
    "dev": "vite",
    "build": "tsc -b && vite build",
    "typecheck": "tsc --noEmit",
    "test": "vitest run",
    "lint": "eslint .",
    "format:check": "prettier --check ."
  }
}

Scripts are the command surface for humans and CI.

Dependency categories
Field	Meaning	Example
dependencies	Needed at runtime	react, express
devDependencies	Needed to build/test/dev	vite, vitest, typescript
peerDependencies	Provided by consumer	react for a React library
optionalDependencies	May be absent	platform-specific package
workspace deps	Local packages	monorepo modules