TopolearnAlmost every Node project starts with package.json and depends on packages from the npm registry.
npm ships with Node and does two jobs: it installs packages from the public registry, and it runs your project's scripts. A project is any folder with a package.json, created with npm init -y.
The fields you will touch most:
name,version— identity, required if you publish.type— set to"module"for ES modules.scripts— named commands:"dev": "node --watch src/server.js","test": "node --test". Run them withnpm run dev;npm testandnpm startare shortcuts.dependencies— packages your code needs at runtime.devDependencies— tools only needed while developing (test helpers, linters, TypeScript).engines— the Node versions you support, e.g.">=22".
Installing:
npm install express # adds to dependencies
npm install -D eslint # adds to devDependencies
npm uninstall express
npx eslint . # run a package's binary without a global installPackages land in node_modules/, a folder you never edit and never commit (add it to .gitignore). Node finds packages there by walking up from the importing file's directory.
Scripts run with node_modules/.bin on the PATH, so "lint": "eslint ." uses the locally installed eslint — no global installs needed, and every developer gets the same version.
Avoid npm install -g for project tools; keep them in devDependencies so the project describes everything it needs. Global installs are fine for personal utilities you use across projects.
Example
# Start a project and add a dependency
mkdir hello-api && cd hello-api
npm init -y
npm pkg set type=module
npm pkg set scripts.dev="node --watch server.js" scripts.test="node --test"
npm install express
npm install -D @types/node
# package.json now contains (abridged):
# {
# "name": "hello-api",
# "type": "module",
# "scripts": { "dev": "node --watch server.js", "test": "node --test" },
# "dependencies": { "express": "^5.1.0" },
# "devDependencies": { "@types/node": "^22.10.0" }
# }
npm run dev # or: node --run dev
npx eslint --versionRemember
- package.json describes the project: type, scripts, dependencies
dependenciesfor runtime,devDependenciesfor tooling- Never edit or commit node_modules;
npxruns local binaries
Watch out for
- Installing project tools globally so the project silently depends on your machine.