node

Node.js JavaScript runtime built on Chrome's V8 engine

TLDR

Run a JavaScript file

$ node [script.js]

Start the REPL (interactive shell)

$ node

Evaluate an expression and print the result

$ node -e "[console.log('hello')]"

Pass arguments to a script (available via `process.argv`)

$ node [script.js] [arg1] [arg2]

Run a script with the inspector enabled and break on first line

$ node --inspect-brk [script.js]

Syntax-check without running

$ node --check [script.js]

Watch and restart on file changes (Node.js 18+)

$ node --watch [script.js]

Run TypeScript with a custom loader

$ node --import [tsx] [script.ts]

Print version

$ node --version

SYNOPSIS

node [options] [v8-options] [script | - | -e string] [arguments]

node is the Node.js JavaScript and (with `--experimental-wasi`) WebAssembly runtime built on the V8 engine. It executes scripts on the server, exposing an event-driven, non-blocking I/O model and a large standard library (`fs`, `http`, `crypto`, `stream`, `child_process`, etc.).Node supports both CommonJS (`require`) and ECMAScript modules (`import`). Module type is determined by the file extension (`.cjs`/`.mjs`) or by the nearest `package.json`'s `"type"` field. Built-in modules can be imported with the `node:` specifier (e.g. `import fs from 'node:fs/promises'`).The interpreter ships with npm and npx for package management, a built-in test runner (`node --test`), worker threads for CPU-bound parallelism, and a built-in debugger and profiler accessible through `--inspect`.

PARAMETERS

-e, --eval CODE

Evaluate code as JavaScript without loading a file.

-p, --print CODE

Like -e but prints the result to stdout.

-r, --require MODULE

Preload module before running the main script (CommonJS only).

--import MODULE

Preload an ES module before running the main script.

-c, --check

Parse the script and check for syntax errors without executing it.

-i, --interactive

Force the REPL even if stdin is not a TTY.

--inspect[=host:port]

Enable the V8 inspector on the given host/port (default 127.0.0.1:9229).

--inspect-brk[=host:port]

Like --inspect but break before user code starts.

--watch

Restart the process when watched files change. (Node.js 18+)

--watch-path PATH

Additional path to watch when --watch is enabled.

--enable-source-maps

Use source maps for stack traces.

--no-warnings

Silence all process warnings (including deprecations).

--max-old-space-size MB

Set the V8 old-generation heap size in megabytes.

--experimental-vm-modules

Enable the experimental ES module API in the `vm` module.

-v, --version

Print Node.js version.

-h, --help

Print Node.js command-line help.

CONFIGURATION

NODE_OPTIONS

Space-separated list of CLI options applied before any explicit ones (e.g. `NODE_OPTIONS="--enable-source-maps"`).

NODE_PATH

Colon-separated list of additional directories searched for CommonJS modules.

NODE_ENV

Convention used by many frameworks; not interpreted by Node itself.

package.json

The presence of `"type": "module"` switches `.js` files to ES modules; `"main"` and `"exports"` define entry points.

CAVEATS

The default event loop is single-threaded — CPU-heavy work blocks all I/O unless offloaded to worker_threads or a child process. Long-term-support (LTS) and current release lines have different feature sets; check `node --version` and the docs before relying on flags such as --watch or --import. Some long-standing flags (like `--loader`) have been replaced by `--import`/`--experimental-loader`.

HISTORY

Node.js was created by Ryan Dahl in 2009. It is now stewarded by the OpenJS Foundation and follows a release schedule of even-numbered LTS lines (e.g. 18, 20, 22) supported for ~30 months and odd-numbered current releases that bring newer V8 features.