api/searchcode.js

export async function GET(request) {
  const body = JSON.stringify({
    grant_type: 'client_credentials',
    client_id: 'your-client_id',
    secret_key: 'your-secret_key'
  })
  const headers = { 'Content-Type': 'application/json', 'x-forwarded-for': '127.0.0.1', 'User-Agent': 'Mozilla/5.0' }
  const tokenRes = await fetch('https://api.da.pf.japanpost.jp/api/v1/j/token', { method: 'POST', headers, body })
  const { token } = await tokenRes.json()
  const search_code = new URL(request.url).searchParams.get('search_code')
  const searchRes = await fetch('https://api.da.pf.japanpost.jp/api/v1/searchcode/' + search_code, { headers: { 'Authorization': 'Bearer ' + token, 'User-Agent': 'Mozilla/5.0' } })
  const res = new Response(searchRes.body, searchRes)
  res.headers.set('Access-Control-Allow-Origin', '*')
  return res
}

vercel.json

{
  "public": true,
  "regions": ["hnd1"],
  "rewrites": [
    { "source": "/:search_code", "destination": "/api/searchcode?search_code=:search_code" }
  ]
}

api.da.pf.japanpost.jpはap-northeast-1のEC2でExpressサーバーで実行されているので、hnd1を指定すると吉

システム登録の固定IPアドレスは127.0.0.1に設定しよう！

'x-forwarded-for': '127.0.0.1'で実行するとAWSでもGCPでもGoogle Apps Scriptでも動く！

使い方

curl https://jp-chi.vercel.app/1000001

await fetch('https://jp-chi.vercel.app/1000001').then(r=>r.json())
{
    "page": 1,
    "limit": 1000,
    "count": 1,
    "searchtype": "zipcode",
    "addresses": [
        {
            "dgacode": null,
            "zip_code": "1000001",
            "pref_code": "13",
            "pref_name": "東京都",
            "pref_kana": "トウキョウト",
            "pref_roma": "TOKYO",
            "city_code": "13101",
            "city_name": "千代田区",
            "city_kana": "チヨダク",
            "city_roma": "CHIYODA-KU",
            "town_name": "千代田",
            "town_kana": "チヨダ",
            "town_roma": "CHIYODA",
            "biz_name": null,
            "biz_kana": null,
            "biz_roma": null,
            "block_name": null,
            "other_name": null,
            "address": null,
            "longitude": null,
            "latitude": null
        }
    ]
}