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A command-line interface (CLI) framework for Node.js and web browser

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The @carnesen/cli package includes runtime JavaScript files (ES2019 + CommonJS) and TypeScript type declarations (3.7+). It has no npm dependencies and is known to work with Node.js 12+ and all modern web browsers.


  • Easy to use: We ❤️ CLIs and want to use them everywhere for everything. This library makes it easy to create beautiful well-behaved CLIs for Node.js and for web browsers.

  • Isomorphic: As far as we know, this is the only isomorphic JavaScript CLI framework. Run your browser CLI in a terminal emulator like our online examples or in the browser's built-in terminal, the JavaScript console!

  • Intelligent types: This is first and foremost a TypeScript library. All components are intelligently typed, and our built-in parsers ensure that the types are respected at runtime.

  • Automatic documentation: Build your CLI with our factories, and we'll automatically generate pretty-good command-line usage out of the box. You can add descriptions and custom <placeholder>s to your command objects too, and we'll automatically fold the text to fit the user's terminal.

  • Built-in ANSI decoration: Bring your CLI to life with our built-in ANSI text decoration methods.

  • Hidden commands Add "hidden=true" to any argument/command/group, and we'll hide it in the automatic usage docs. We use this feature for easter eggs and internal/beta commands.

  • Automatic autocomplete (Coming soon!): Autocomplete supercharges a CLI. We've implemented automatic autocomplete in the live examples and plan to add this as a feature to the core library for the next release.


This library has 100% test coverage and heavy usage by its authors but should be considered 0.x beta software.

More information

Questions, bugs, feature requests? Please file an issue or submit a pull request on this project's repository on GitHub, and check out our:


MIT © Chris Arnesen


Install this library using npm:

npm install @carnesen/cli

Here is a TypeScript Node.js CLI that does some basic arithmetic:

// src/multiply.ts
import {
} from '@carnesen/cli';

const multiplyCommand = CliCommand({
   name: 'multiply',
   description: 'Multiply numbers and print the result',
   positionalArgGroup: CliNumberArrayArgGroup({
      required: true,
   action({ positionalValue: numbers }) {
      return numbers.reduce((a, b) => a * b, 1);

// Export for unit testing
export const cli = Cli(multiplyCommand);

// If this module is the entrypoint for this Node.js process
if (require.main === module) {

Here's how that Node.js CLI behaves in a terminal:

Multiply CLI in Node.js

The only Node.js-specific code is the if (require.main === module) block. To instead make a web browser console CLI, replace that with:

(window as any).multiply = (line: string) => {

Here's that CLI in a JavaScript console:

Multiply CLI in a web browser console

The resolved value of 0 means the command finished successfully. A non-zero exit code means an error occurred. Try it you yourself at cli.carnesen.com! Here's how to open the console in Firefox and Google Chrome.


The general structure of a @carnesen/cli command line is:

<command group> <command> \
   <positional-args> \
   --name <args> \
   -- <double-dash-args>

Only <command> is required. This section of the documentation describes each of these pieces in more detail.


A command defines an action function or async function together with its command-line arguments. For example, in cloud users list, the command is list. Some commands don't have any arguments. For example:

import { CliCommand } from '@carnesen/cli';

export const listUsersCommand = CliCommand({
   name: 'list',
   async action() {
      // Fetch all users

CliCommand is a factory function (not a constructor) that returns an object of shape ICliCommand.

Most commands define arguments through the positionalArgGroup, namedArgGroups, and/or doubleDashArgGroup properties as described below.

Command group

You can use command groups to organize the commands in your CLI. For example, in cloud users list, cloud and users are command groups and list is a command. Command groups are optional. Organize your CLI to suit your needs and taste:

  • list-cloud-users: No command groups
  • cloud list-users: A single command group
  • cloud users list: A hierarchical command tree
import { CliCommandGroup } from '@carnesen/cli';
import { listUsersCommand } from './list-users-command';

export const usersCommandGroup = CliCommandGroup({
   name: 'users',
   subcommands: [ listUsersCommand ]

export const rootCommandGroup = CliCommandGroup({
   name: 'cloud',
   subcommands: [ usersCommandGroup ]

CliCommandGroup is a factory function (not a constructor) that returns an object of shape ICliCommandGroup.

Positional arguments

A command's positionalArgGroup receives all the command-line arguments after the command but before the first argument that starts with --. For example, in cloud users delete carl karen --force, the positional arguments are carl and karen. The argument group's parsed value is the positionalValue property of the action input:

import { CliCommand, CliStringArrayArgGroup } from '@carnesen/cli';

export const deleteCommand = CliCommand({
   name: 'delete',
   positionalArgGroup: CliStringArrayArgGroup({ required: true }),
   async action({ positionalValue: usernames }) {
      // The CliStringArrayArgGroup parser returns an array of strings e.g.
      //   ["carl", "karen"]
      // Delete the users ...

The CliStringArrayArgGroup parser throws a CliUsageError when required == true and no argument is provided. Conversely, if required == false and no argument is provided, positionalValue is undefined.

Named arguments

A command's namedArgGroups receives all the command-line arguments of the form --name value. The parsed values are passed into the command's action as a property called namedValues of shape { name: <value>, ... }. For example, in cloud users list let's add a command-line flag to filter out inactive users:

import { CliCommand, CliFlagArgGroup } from '@carnesen/cli';

export const listCommand = CliCommand({
   name: 'list',
   namedArgGroups: {
      active: CliFlagArgGroup(),
   async action({ namedValues: { active } }) {
      // CliFlagArgGroup returns false unless --active was passed
      // Fetch the users ...

Double-dash arguments

All command-line arguments after a lone -- are passed to the command's doubleDashArgGroup. After the lone --, things like --name aren't interpreted as argument group separators. This is particularly useful for passing arguments through to another CLI like do -- git --version. The argument group's return value is the doubleDashValue property of the action's input:

import { CliCommand, CliStringArrayArgGroup } from '@carnesen/cli';

export const doCommand = CliCommand({
   name: 'do',
   doubleDashArgGroup: CliStringArrayArgGroup(),
   async action({ doubleDashValue: args }) {
      // Do stuff ...

Error handling

By default, @carnesen/cli console.error's the full exception thrown by the action function or argument parser, stack trace and all. Two special error objects have non-default handling:

  • CliUsageError: Throw this if you want to print the selected command's usage and exit without showing a stack trace. This is useful for defining custom argument parsers.
  • CliTerseError: Throw this if you want to prints the object's message and exit without showing a stack trace

In any case, the command runner exits (returns) a non-zero numeric status code (1) or the thrown exception's exitCode if it's a number. CliTerseError's second argument is exitCode.

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