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argparse

CI NPM version

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

Following code is a JS program that takes a list of integers and produces either the sum or the max:

const { ArgumentParser } = require('argparse')

const parser = new ArgumentParser({ description: 'Process some integers.' })

let sum = ints => ints.reduce((a, b) => a + b)
let max = ints => ints.reduce((a, b) => a > b ? a : b)

parser.add_argument('integers', { metavar: 'N', type: 'int', nargs: '+',
                                  help: 'an integer for the accumulator' })
parser.add_argument('--sum',    { dest: 'accumulate', action: 'store_const',
                                  const: sum, default: max,
                                  help: 'sum the integers (default: find the max)' });

let args = parser.parse_args()
console.log(args.accumulate(args.integers))

Assuming the JS code above is saved into a file called prog.js, it can be run at the command line and provides useful help messages:

$ node prog.js -h
usage: prog.js [-h] [--sum] N [N ...]

Process some integers.

positional arguments:
  N           an integer for the accumulator

optional arguments:
  -h, --help  show this help message and exit
  --sum       sum the integers (default: find the max)

When run with the appropriate arguments, it prints either the sum or the max of the command-line integers:

$ node prog.js 1 2 3 4
4
$ node prog.js 1 2 3 4 --sum
10

If invalid arguments are passed in, it will issue an error:

$ node prog.js a b c
usage: prog.js [-h] [--sum] N [N ...]
prog.js: error: argument N: invalid 'int' value: 'a'

This is an example ported from Python. You can find detailed explanation here.

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.

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