When no subcommands are provided, print help? about argparse HOT 2 CLOSED

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

let argparse = require('./')

// create the top-level parser
let parser = argparse.ArgumentParser('PROG')
parser.add_argument('--foo',{ action: 'store_true', help: 'foo help' })
let subparsers = parser.add_subparsers({help: 'sub-command help'})

// create the parser for the "a" command
let parser_a = subparsers.add_parser('a', {help: 'a help'})
parser_a.add_argument('bar',{ type: 'int', help: 'bar help'})

// create the parser for the "b" command
let parser_b = subparsers.add_parser('b', {help: 'b help'})
parser_b.add_argument('--baz', {choices: 'XYZ', help: 'baz help'})
// print main help
console.log(parser.format_help())

// retrieve subparsers from parser
let subparsers_actions = parser._actions
  .filter(a => a.constructor.name === '_SubParsersAction')

// there will probably only be one subparser_action,
// but better safe than sorry
for (let subparsers_action of subparsers_actions) {
    // get all subparsers and print help
    for (let [ choice, subparser ] of Object.entries(subparsers_action.choices)) {
        console.log(`Subparser '${choice}'`)
        console.log(subparser.format_help())
    }
}