[js: object / keys - Object.fromEntries] Create Object by Arrays. #js

inferable-object-keys.ts

/**
 * type inferable Object.keys
 *
 * NOTE key が number な型定義だと number[] になりつつ
 *      「 js の object key は全て string 」という仕様で
 *      string[] になるので、後続で map(Number) など必要
 */
export const objectKeys = <T extends object>(target: T): (keyof T)[] => (
  Object.keys(target).map(key => key as keyof T)
)

/**
 * objectByKeys との組み合わせで json の keys を
 * string union で型定義しつつバラしたり
 */
import { issues as issuesData } from 'data.json' // 何らか固定データ

export type Issue = {
  key: keyof typeof issuesData
  subject: string
}

export const issues: Record<Issue['key'], Issue> = (
  objectByKeys(objectKeys(issuesData), key => ({
    key,
    subject: issuesData[key].subject.trim(), // 整形してシステム取り込み的な
  }))
)

console.log(
  issues['型推論可能なキー'].subject
)

object-by-keys.ts

/**
 * @example
 *   objectByKeys([1, 2, 3])
 *   //=> { '1': undefined, '2': undefined, '3': undefined }
 *
 *   objectByKeys([1, 2, 3], 'initial')
 *   // => { '1': 'initial', '2': 'initial', '3': 'initial' }
 *
 *   objectByKeys([1, 2, 3], key => Number(key))
 *   // => { '1': 1, '2': 2, '3': 3 }
 *
 * @link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries
 * @link https://zenn.dev/yano3nora/articles/cb00fad3b445c0
 */
export const objectByKeys = <T extends string|number|symbol, U = undefined>(
  keys: T[],
  initial?: U | ((key: T) => U),
): Record<T, U> => Object.fromEntries([
    ...keys.map(key => [
      key,
      initial instanceof Function ? initial(key) : initial,
    ])
  ])