Convert SF 15 char to 18 char id

15to18.js

(inp) =>
  ((elements) =>
    inp.length != 15
      ? Error("invalid id")
      : inp +
        Object.values(elements)
          .map((a) => "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345".charAt(a))
          .join(""))(
    inp.split("").reduce(
      (op, curr, index) => {
        curr >= "A" &&
          curr <= "Z" &&
          (op[Math.floor(index / 5)] += 1 << index % 5);
        return op;
      },
      { 0: 0, 1: 0, 2: 0 }
    )
  );