port_difference.md

Differences with python version

1. Option object instead of keyword arguments

Python:

# python allows keyword arguments
parser = argparse.ArgumentParser(prog='PROG', usage='%(prog)s [options]')

Javascript:

// keyword arguments are passed as a single `options` object
parser = argparse.ArgumentParser({ prog: 'PROG', usage: '%(prog)s [options]' })

2. Use strings 'int', 'float' or 'str' instead of built-in python types

Python:

parser.add_argument('--foo', type=int)

Javascript:

parser.add_argument('--foo', { type: 'int' })

3. TypeError instead of ValueError

Python raises TypeError or ValueError for various argument errors. Javascript raises TypeError in both cases.

4. FileType() returns a stream

You should be closing it with .close() if available (which doesn't exist for stdin/stdout).

5. When class is called as a function, .call is executed

Override Action.call instead of Action.__call__ in inherited classes

6. Limited support for %-formats

• %s is rendered as String(arg)
• %r is rendered as util.inspect(arg)
• %d, %i is rendered as arg.toFixed(0), no precision digits or padding is supported
• no other formats are implemented yet

7. No gettext support

All error messages are hardcoded.