Node.js JavaScript runtime CLI

Version 20.19.5 · source

Postcard A5 A4 A4 landscape A3 A3 landscape Letter Tabloid

Light · Postcard 102 × 152 mm · PDF

Dark · Postcard 102 × 152 mm · PDF

Ink saver · Postcard 102 × 152 mm · PDF

Light · A5 148 × 210 mm · PDF

Dark · A5 148 × 210 mm · PDF

Ink saver · A5 148 × 210 mm · PDF

Light · A4 210 × 297 mm · PDF

Dark · A4 210 × 297 mm · PDF

Ink saver · A4 210 × 297 mm · PDF

Light · A4 landscape 297 × 210 mm · PDF

Dark · A4 landscape 297 × 210 mm · PDF

Node.js, A4 landscape, ink saver preview

Ink saver · A4 landscape 297 × 210 mm · PDF

Light · A3 297 × 420 mm · PDF

Dark · A3 297 × 420 mm · PDF

Ink saver · A3 297 × 420 mm · PDF

Light · A3 landscape 420 × 297 mm · PDF

Dark · A3 landscape 420 × 297 mm · PDF

Node.js, A3 landscape, ink saver preview

Ink saver · A3 landscape 420 × 297 mm · PDF

Light · Letter 8.5 × 11 in · PDF

Dark · Letter 8.5 × 11 in · PDF

Ink saver · Letter 8.5 × 11 in · PDF

Light · Tabloid 11 × 17 in · PDF

Dark · Tabloid 11 × 17 in · PDF

Ink saver · Tabloid 11 × 17 in · PDF

Start here

node <file>

Run a script

node

Open the REPL

node -e "<code>"

Run a one-liner

node -p "<expr>"

Evaluate and print

node --watch <file>

Restart on change

node --test

Run the tests

node --env-file=.env <file>

Load a .env file

node --inspect-brk <file>

Debug in DevTools

Concepts

NODE_OPTIONS environment defaults
Node flags node --watch ...
Script file.js or -e
Arguments process.argv

Run code

node <file>

Run a script

node

Start the interactive REPL

node -e "<code>"

Evaluate a string of code

node -p "<expr>"

Evaluate and print the result

node <file> <args>

Pass arguments to the script

Read them from process.argv.slice(2).

node -

Read the script from stdin

node -c <file>

Syntax check without running

node --input-type=module -e "<code>"

Evaluate code as an ES module

Allows import and top-level await in -e.

node -v

Print the Node version

corepack enable

Activate pnpm and yarn shims

Bundled with Node 20 and 22; not with Node 25+.

node -p "process.versions"

Show V8 and library versions

Watch mode

node --watch <file>

Restart when imported files change

node --watch-path=<dir> <file>

Watch specific paths instead

Implies --watch. Recursive watching is only supported on macOS and Windows.

node --watch-preserve-output <file>

Keep the console between restarts

Test runner

node --test

Run all discovered test files

Finds *.test.js, test/**, and similar patterns.

node --test <file>

Run specific test files

node --test-name-pattern="<regex>"

Run tests whose name matches

node --test-only

Run only tests marked only

node --test-reporter=<name>

Choose output: spec, tap, dot, junit

node --test --watch

Re-run tests on change

Minimal test file

import test from 'node:test';import assert from 'node:assert/strict';test('adds', () => {  assert.equal(1 + 1, 2);});

Environment and config

node --env-file=<file> <script>

Load variables from a .env file

Repeat the flag to load several files; later ones win.

NODE_OPTIONS="<flags>" node
                    <script>

Set default flags via environment

NODE_ENV=production node <script>

Set a variable for one run

Only a convention that libraries read; Node itself ignores it.

node --require <module>

Preload a CommonJS module

node --import <module>

Preload an ES module

node --run <script>

Run a package.json script

Node 22+. Faster than npm run but has no lifecycle hooks.

node --title=<name> <script>

Set the process title

Debugging

node --inspect <file>

Start with the inspector open

Then open chrome://inspect or attach an editor on port 9229.

node --inspect-brk <file>

Break on the first line

node inspect <file>

Use the built-in CLI debugger

node --enable-source-maps <file>

Map stack traces to source files

node --trace-warnings <file>

Show where warnings come from

node --trace-deprecation <file>

Show where deprecated APIs are used

node --no-warnings <file>

Silence all process warnings

NODE_DEBUG=<module> node <file>

Log internals, e.g. http, fs

Performance and memory

node --max-old-space-size=<MiB> <file>

Raise the heap limit

Fixes JavaScript heap out of memory crashes.

node --v8-options

List all V8 flags

Permissions and TypeScript

node --permission --allow-fs-read=<path>
                    <file>

Restrict file access

Flag is --experimental-permission before Node 22.13 and 23.5.

node <file>.ts

Run TypeScript by stripping types

Default in Node 22.18+ and 23.6+; use --experimental-strip-types on 22.6+. No enums or paths.

node --no-strip-types

Turn off TypeScript support

REPL

Dot commands

Command	Effect
`.help`	List commands
`.editor`	Multi-line editor, Ctrl+D runs
`.load <file>`	Run a file in the session
`.save <file>`	Save the session to a file
`.break`	Abandon a multi-line input
`.exit`	Leave (or Ctrl+D)

Tab

Complete names and properties

_

Last evaluated result

Recipes

One-liners

# random UUIDnode -p "crypto.randomUUID()"# today as ISO datenode -p "new Date().toISOString()"# usable CPU countnode -p "os.availableParallelism()"

Dev loop with env and watch

node --watch --env-file=.env server.js# tests alongsidenode --test --watch

Debug a failing test

node --inspect-brk --test --test-name-pattern="adds" test/a.test.js# then open chrome://inspect