path and process

Two built-in features you’ll use in almost every Node.js project: the path module for working with file system paths, and the process global for runtime information.

The path module

File paths look different on Windows (C:\Users\alice\file.txt) and Unix (/home/alice/file.txt). The path module handles this automatically.

import { join, resolve, dirname, basename, extname } from 'path'

path.join

Joins path segments with the correct separator for the OS:

import { join } from 'path'

const dbPath = join(process.cwd(), 'data', 'bulletin.db')
// Unix: '/home/user/project/data/bulletin.db'
// Windows: 'C:\Users\user\project\data\bulletin.db'

Always use path.join instead of string concatenation for paths.

path.resolve

Resolves a sequence of paths into an absolute path, starting from the current working directory:

import { resolve } from 'path'

resolve('src', 'index.ts')
// → '/absolute/path/to/project/src/index.ts'

path.dirname, path.basename, path.extname

import { dirname, basename, extname } from 'path'

const filePath = '/home/alice/project/src/index.ts'

dirname(filePath)    // '/home/alice/project/src'
basename(filePath)   // 'index.ts'
extname(filePath)    // '.ts'
basename(filePath, extname(filePath)) // 'index' (name without extension)

The process object

process is a global available in every Node.js file — no import needed. It provides information about the running process.

process.cwd()

The current working directory — the directory from which you ran node:

console.log(process.cwd())
// → '/home/user/bulletin-api'

Use this to build absolute paths that work regardless of where you require/import from:

const dbPath = join(process.cwd(), 'bulletin.db')

process.env

A dictionary of environment variables. This is how configuration values (database paths, JWT secrets, ports) are passed to Node.js without hardcoding them:

const port = process.env.PORT || '3000'
const jwtSecret = process.env.JWT_SECRET

if (!jwtSecret) {
  throw new Error('JWT_SECRET environment variable is required')
}

process.argv

Command-line arguments passed to the script:

// node script.ts --migrate --seed
console.log(process.argv)
// ['node', '/path/to/script.ts', '--migrate', '--seed']

Useful for build scripts and migration utilities.

process.exit()

Exits the Node.js process with a status code:

process.exit(0)  // success
process.exit(1)  // error (non-zero = failure for CI/CD)

process.on('uncaughtException')

Handle unexpected errors that weren’t caught anywhere:

process.on('uncaughtException', (error) => {
  console.error('Uncaught exception:', error)
  process.exit(1)
})

In production, use a proper error monitoring service — but this prevents silent crashes during development.

In the Bulletin API

The API uses path and process throughout:

src/db/index.ts

import { join } from 'path'
import Database from 'better-sqlite3'

const dbPath = process.env.DATABASE_PATH || join(process.cwd(), 'bulletin.db')
const db = new Database(dbPath)

src/index.ts

const PORT = parseInt(process.env.PORT || '3000', 10)
app.listen(PORT, () => console.log(`API running on port ${PORT}`))

Exercise

1. Create src/utils/paths.ts that exports a paths object with absolute paths for common project directories: root, src, db.
2. Use process.cwd() and path.join to build these.
3. Log the paths and verify they’re correct absolute paths.
4. Add a check: if process.env.NODE_ENV isn’t set, log a warning.

Recap

• path.join(...) builds cross-platform paths — always use it instead of string concatenation.
• path.resolve(...) creates absolute paths from the current directory.
• process.cwd() is the directory from which the script was run.
• process.env holds environment variables — use it for configuration.
• process.argv has command-line arguments; process.exit(code) terminates the process.