argparse/README.md

CLI arguments parser. Native port of python's argparse.

argparse
========

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CLI arguments parser for node.js, with [sub-commands](https://docs.python.org/3.14/library/argparse.html#sub-commands) support. Port of python's [argparse](https://docs.python.org/3.14/library/argparse.html) (version [3.14.6](https://github.com/python/cpython/blob/v3.14.6/Lib/argparse.py)).

**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()`.

See the complete list of [differences from Python](./doc/port_difference.md).
Users upgrading from v2 should read the [migration guide](./doc/migrate_v2_to_v3.md).


Example
-------

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

```js
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

options:
  -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](https://docs.python.org/3.14/library/argparse.html).


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](https://docs.python.org/3.14/library/argparse.html).
2. [Original tutorial](https://docs.python.org/3.14/howto/argparse.html).
3. [Differences from Python](./doc/port_difference.md).
4. [Migration from v2 to v3](./doc/migrate_v2_to_v3.md).