26 line forgiving argv parser

argvParser.js

const VALUES = Symbol('VALUES');

const Parser = (argv, { subcommands } = {}) => {
	argv = argv.slice(2);
	return {
		get (key) {
			if (key === VALUES) {
				return argv.filter((x, i) =>
					(!subcommands || i !== 0) && !x.startsWith('-')
					&& (!argv[i - 1] || !argv[i - 1].startsWith('-')));
			} else if (key.startsWith('-')) {
				if (key.startsWith('--')) {
					const i = argv.findIndex(x => x === key);
					if (i === -1) return null;
					if (argv[i + 1] && !argv[i+1].startsWith('-'))
						return argv[i + 1];
					return true;
				}
			} else {
				if (subcommands && argv[0] === key)
					return argv.slice(1).findIndex(x => x === key) !== -1;
				if (argv.findIndex((x, i) =>
					x === key && (!argv[i - 1] || !argv[i-1].startsWith('-'))
				) !== -1) return true;
			}
			return null;
		}
	};
};

/* -- */
const parser = Parser(process.argv);
console.log(parser.get("--thing"));
/* -- */

module.exports = Parser;
module.exports.VALUES = VALUES;