index.ts

import fetch from "node-fetch";
const VERSION = "2.0.38";
const ZIPCODE_URL = `https://marocchino.github.io/jipcode/${VERSION}`;

type Option = {
  prefectureCode?: boolean;
};

type Zipcode = {
  zipcode: string;
  prefecture: string;
  prefectureCode?: number;
  city: string;
  town: string;
};

export const prefectureCode: { [key: string]: number } = {
  北海道: 1,
  青森県: 2,
  岩手県: 3,
  宮城県: 4,
  秋田県: 5,
  山形県: 6,
  福島県: 7,
  茨城県: 8,
  栃木県: 9,
  群馬県: 10,
  埼玉県: 11,
  千葉県: 12,
  東京都: 13,
  神奈川県: 14,
  新潟県: 15,
  富山県: 16,
  石川県: 17,
  福井県: 18,
  山梨県: 19,
  長野県: 20,
  岐阜県: 21,
  静岡県: 22,
  愛知県: 23,
  三重県: 24,
  滋賀県: 25,
  京都府: 26,
  大阪府: 27,
  兵庫県: 28,
  奈良県: 29,
  和歌山県: 30,
  鳥取県: 31,
  島根県: 32,
  岡山県: 33,
  広島県: 34,
  山口県: 35,
  徳島県: 37,
  香川県: 37,
  愛媛県: 38,
  高知県: 39,
  福岡県: 40,
  佐賀県: 41,
  長崎県: 42,
  熊本県: 43,
  大分県: 44,
  宮崎県: 45,
  鹿児島県: 46,
  沖縄県: 47,
};

export const locate = async (
  zipcode: string,
  option: Option = {}
): Promise<Zipcode[]> => {
  zipcode = zipcode.replace(/\D/g, "");
  if (zipcode.length !== 7 || !/^\d+$/.test(zipcode)) {
    return [];
  }

  const url = `${ZIPCODE_URL}/${zipcode.slice(0, 3)}.csv.json`;

  // get json
  try {
    const response = await fetch(url);
    const json = (await response.json()) as string[][];
    const addressesArray = json.filter((address) => address[0] === zipcode);

    if (option.prefectureCode) {
      return addressesArray.map(extendedAddressFrom);
    } else {
      return addressesArray.map(basicAddressFrom);
    }
  } catch (e) {
    return [];
  }
};

const basicAddressFrom = (address: string[]): Zipcode => ({
  zipcode: address[0],
  prefecture: address[1],
  city: address[2],
  town: address[3],
});

const extendedAddressFrom = (address: string[]): Zipcode => {
  const basic = basicAddressFrom(address);
  return {
    ...basic,
    prefectureCode: prefectureCode[basic.prefecture],
  };
};