@hamlog/maidenhead/dist/index.js

For various amateur radio needs, we at [Hamlog.Online](https://hamlog.online) required a library to process [Maidenhead grid locators](https://en.wikipedia.org/wiki/Maidenhead_Locator_System) in Javascript.

function d(e) {
  if (e.length % 2 !== 0) return !1;
  const t = e.toLowerCase();
  if (!/^[a-x0-9]+$/.test(t)) return !1;
  for (let r = 0; r < t.length; r += 2) {
    const n = `${t[r]}${t[r + 1]}`;
    if (r == 0) {
      if (!/[a-r]{2}/.test(n))
        return !1;
    } else if (r % 4 != 0) {
      if (!/\d{2}/.test(n))
        return !1;
    } else if (!/[a-x]{2}/.test(n))
      return !1;
  }
  return !0;
}
const f = 65, h = 48;
function u(e) {
  let t = e.charCodeAt(0);
  return t >= f ? t - f : t - h;
}
function c(e, t) {
  return String.fromCharCode(e + (t ? f : h));
}
function p(e) {
  if (!d(e))
    throw new SyntaxError(`"${e}" is not a valid Maidenhead locator`);
  const t = e.toUpperCase(), r = t.length / 2;
  let n = -90, a = -90, l = 10;
  for (let o = 0; o < r; o++)
    n += l * u(t[2 * o]), a += l * u(t[2 * o + 1]), o < r - 1 && (o % 2 > 0 ? l /= 24 : l /= 10);
  return n *= 2, [
    {
      lat: a,
      lon: n
    },
    {
      lat: a + l,
      lon: n + l * 2
    }
  ];
}
function x(e) {
  const t = p(e);
  return {
    lat: (t[0].lat + t[1].lat) / 2,
    lon: (t[0].lon + t[1].lon) / 2
  };
}
function C(e) {
  let t = "";
  for (let r = 0; r < e.length; r++)
    t += [4, 5, 12, 13].includes(r) ? e[r].toLowerCase() : e[r].toUpperCase();
  return t;
}
function v(e, t = 6, r = !1) {
  if (t % 2 != 0)
    throw SyntaxError(
      "Maidenhead grids are supposed to have an even number of characters."
    );
  let n = "", a = e.lon / 2 + 90, l = e.lat + 90, o = 10;
  for (let i = 0; i <= 6; i++) {
    const s = i % 2 == 0;
    n += c(Math.floor(a / o), s), n += c(Math.floor(l / o), s), a %= o, l %= o, i % 2 > 0 ? o /= 24 : o /= 10;
  }
  return r && (n = C(n)), n.slice(0, t);
}
export {
  p as gridToBox,
  x as gridToPoint,
  v as pointToGrid,
  d as validateGrid
};