Consistent Arrays from Query Params with Express and Archetype

example.js

const Archetype = require('archetype');
const express = require('express');
const superagent = require('superagent');

const app = express();

const Params = new Archetype({
  names: { $type: ['string'], $default: [] }
}).compile('Params');
app.get('/', function(req, res) {
  res.json(new Params(req.query));
});

run().catch(error => console.error(error));

async function run() {
  await app.listen(3000);

  const root = 'http://localhost:3000';
  // {"names":[]}
  console.log(await superagent.get(`${root}`).then(res => res.text)); 
  // {"names":["test"]}
  console.log(await superagent.get(`${root}?names=test`).then(res => res.text));
  // {"names":["batman","robin"]}
  console.log(await superagent.get(`${root}?names=batman&names=robin`).then(res => res.text));
}