Data Archive

npm

npm is the package manager for the JavaScript ecosystem, primarily used with Node.js.

Core role

npm manages dependencies for JavaScript projects. It allows you to:

  • Install third-party libraries
  • Version and lock those libraries
  • Publish and distribute your own packages
  • Define and run project-specific commands

Conceptually, it plays the same role that pip plays in Python.

Key components

1. Package registry

A public registry containing millions of packages, each identified by a name and version. Packages typically expose reusable code, tooling, or frameworks.

2. CLI tool

The npm command-line interface is installed automatically with Node.js.

Common commands:

  • npm init — create a package.json
  • npm install <package> — add a dependency
  • npm install — install all declared dependencies
  • npm run <script> — execute a project script

3. package.json

A manifest file that defines:

  • Project metadata
  • Dependencies and version ranges
  • Scripts (custom commands)
  • Configuration hints for tools

Example:

{
  "name": "example-project",
  "version": "1.0.0",
  "dependencies": {
    "lodash": "^4.17.21"
  },
  "scripts": {
    "build": "node build.js"
  }
}

4. Lock file

package-lock.json records the exact dependency versions installed, ensuring reproducible builds across machines and environments.

Dependency types

  • dependencies — runtime requirements
  • devDependencies — build, test, lint tooling
  • peerDependencies — compatibility contracts (common in libraries)

Versioning follows semantic versioning: .

Typical use cases

  • Frontend frameworks (React, Vue, Svelte)
  • Backend services (Express, Fastify)
  • Build tools (Vite, Webpack, ESLint, Prettier)
  • Data tooling and CLIs

Relation to alternatives

  • yarn and pnpm are alternative package managers that use the same registry but differ in performance and dependency resolution strategy.
  • npm remains the default and most widely supported.

Mental model

Think of npm as:

A reproducible dependency graph manager + task runner for JavaScript projects.

If useful, I can next:

  • Contrast npm with pip in terms of dependency resolution
  • Walk through a minimal Node.js project structure
  • Explain lockfiles and semver edge cases in detail

Backlinks