agegate/src/index.js

A simple function that verifies a date of birth against a country's legal drinking age.

import data from "./countries.js";

// Flatten continent-grouped country data into a simpler map.
export const getData = () => Object.values(data).reduce((a, b) => a.concat(b));
const countries = getData();

const DEFAULT_LEGAL_AGE = 18;

// Age calculator by Lucas Janon.
// https://stackoverflow.com/a/50827764/362136
const getAge = (date) =>
  Math.floor((new Date() - new Date(date).getTime()) / 3.15576e10);

function agegate(date, countryCode) {
  const age = getAge(date);
  const country = countries.find((c) => c.code === countryCode.toUpperCase());

  // null country age value indicates alcohol prohibition
  if ((country && country.age === null) || isNaN(age)) {
    return false;
  }

  const ageLimit = country ? country.age : DEFAULT_LEGAL_AGE;
  return age >= ageLimit;
}

export default agegate;