API

Overview of the client returned by createLocalGovClient.

`createLocalGovClient(options)`

Option	Description
`data`	npm dataset (or equivalent object)
`url`	Versioned URL to `index.json`
`cache`	localStorage cache for `url` mode. Default `true`
`cacheTtlSeconds`	Cache TTL in seconds. Default `31536000` (1 year)

Exactly one of data or url is required. cache / cacheTtlSeconds apply to url mode (unused for URL caching when using data).

Method	Returns	Description
`listPrefectures()`	`LocalGov[]`	All prefectures
`getPrefectureByCode(code)`	`LocalGov \| null`	Lookup by prefecture code
`getPrefectureCodeByName(name)`	`string \| null`	Prefecture code from exact name
`listMunicipalitiesByPrefecture(pref, options?)`	`Promise<LocalGov[]>`	Municipalities in a prefecture (lazy)
`getMunicipalityByCode(code)`	`Promise<LocalGov \| null>`	Lookup by 6-digit municipality code
`getByCode(code)`	`Promise<LocalGov \| null>`	Auto-detect 2-digit / 6-digit
`searchByText(text, options?)`	`Promise<LocalGov[]>`	Partial-match search
`getLocalGovCodeByName(name, options?)`	`Promise<string \| null>`	Code from exact name

Filters designated-city bodies vs administrative wards. Default is "both". Tokyo special wards (e.g. 千代田区) are not affected.

Value	Meaning
`"both"`	City body and wards (default)
`"city"`	City body only (exclude wards)
`"ward"`	Wards only (exclude city bodies)

Applies to: listMunicipalitiesByPrefecture / searchByText / getLocalGovCodeByName

Key	Type	Default	Description
`designatedCity`	`'both' \| 'city' \| 'ward'`	`'both'`	Designated-city body/ward filter

Key	Type	Default	Description
`prefecture`	`string`	—	Filter by prefecture
`target`	`'all' \| 'prefectures' \| 'cities'`	`'all'`	Search target
`matchField`	`'name' \| 'nameKana' \| 'both'`	`'both'`	Fields to match
`designatedCity`	`'both' \| 'city' \| 'ward'`	`'both'`	Designated-city body/ward filter

String search normalizes hiragana / fullwidth kana to halfwidth kana.