argparse

What is argparse?

The argparse npm package is a node.js module for parsing command-line options and arguments. It is inspired by the Python argparse module and allows developers to create user-friendly command-line interfaces for their applications. It provides a way to specify what arguments the program requires, and parses those arguments from the process.argv array.

What are argparse's main functionalities?

Argument Parsing

This feature allows the program to parse command-line arguments. The code sample demonstrates how to create a new ArgumentParser, add arguments with options like verbosity, and then parse the arguments provided by the user.

const { ArgumentParser } = require('argparse');
const parser = new ArgumentParser({
  description: 'Argparse example'
});

parser.add_argument('-v', '--verbose', {
  help: 'increase output verbosity',
  action: 'store_true'
});
parser.add_argument('echo', {
  help: 'echo the string you use here'
});

const args = parser.parse_args();
console.log(args);

Sub-commands

This feature allows the program to define sub-commands, which are commands that the program can perform. The code sample shows how to create sub-commands for starting and stopping a service, with additional options for each sub-command.

const { ArgumentParser } = require('argparse');
const parser = new ArgumentParser({
  description: 'Sub-command example'
});

const subparsers = parser.add_subparsers({
  title: 'subcommands',
  dest: 'subcommand_name'
});

const start = subparsers.add_parser('start', { aliases: ['run'] });
start.add_argument('-s', '--service', { help: 'Start the service' });

const stop = subparsers.add_parser('stop');
stop.add_argument('-f', '--force', { help: 'Force stop', action: 'store_true' });

const args = parser.parse_args();
console.log(args);

Argument Types and Choices

This feature allows the program to specify the type of an argument and restrict it to a set of choices. The code sample demonstrates how to define an integer argument and a string argument that must be one of the specified choices.

const { ArgumentParser } = require('argparse');
const parser = new ArgumentParser({
  description: 'Argument types example'
});

parser.add_argument('square', {
  help: 'display a square of a given number',
  type: 'int'
});
parser.add_argument('--cuisine', {
  help: 'choose the type of cuisine',
  choices: ['Italian', 'Mexican', 'Japanese'],
  required: true
});

const args = parser.parse_args();
console.log(args);

Other packages similar to argparse

commander

Commander is another popular npm package for command-line interfaces. It provides a high-level way to specify commands and options, and it automatically generates help messages. Commander is known for its simplicity and declarative style of defining command-line options.

yargs

Yargs is a node.js library that helps build interactive command-line tools, by parsing arguments and generating an elegant user interface. It comes with features like command chaining, automatic help generation, and more. Yargs is often praised for its fluent API and its support for advanced features like command-specific configurations.

minimist

Minimist is a minimalistic argument parsing library. It is designed to be simple and straightforward, with fewer features than argparse, commander, or yargs. It is a good choice for those who need something lightweight without the need for complex command-line interfaces.

README

argparse

CLI arguments parser for node.js, with sub-commands support. Port of python's argparse (version 3.9.0).

Difference with original.

• JS has no keyword arguments support.
  • Pass options instead: new ArgumentParser({ description: 'example', add_help: true }).
• JS has no python's types int, float, ...
  • Use string-typed names: .add_argument('-b', { type: 'int', help: 'help' }).
• %r format specifier uses require('util').inspect().

More details in doc.

Example

test.js file:

#!/usr/bin/env node
'use strict';

const { ArgumentParser } = require('argparse');
const { version } = require('./package.json');

const parser = new ArgumentParser({
  description: 'Argparse example'
});

parser.add_argument('-v', '--version', { action: 'version', version });
parser.add_argument('-f', '--foo', { help: 'foo bar' });
parser.add_argument('-b', '--bar', { help: 'bar foo' });
parser.add_argument('--baz', { help: 'baz bar' });

console.dir(parser.parse_args());

Display help:

$ ./test.js -h
usage: test.js [-h] [-v] [-f FOO] [-b BAR] [--baz BAZ]

Argparse example

optional arguments:
  -h, --help         show this help message and exit
  -v, --version      show program's version number and exit
  -f FOO, --foo FOO  foo bar
  -b BAR, --bar BAR  bar foo
  --baz BAZ          baz bar

Parse arguments:

$ ./test.js -f=3 --bar=4 --baz 5
{ foo: '3', bar: '4', baz: '5' }

API docs

Since this is a port with minimal divergence, there's no separate documentation. Use original one instead, with notes about difference.

1. Original doc.
2. Original tutorial.
3. Difference with python.

argparse for enterprise

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Changelog

[2.0.1] - 2020-08-29

Fixed

• Fix issue with process.argv when used with interpreters (coffee, ts-node, etc.), #150.