cra-template-pi/template/src/i18n/index.ts

A quick start Create React App with many auto implemented features

import messages from './en.json'

type FilterStartingWith<
  Set,
  Needle extends string
> = Set extends `${Needle}${infer _X}` ? _X : never

type FilterBetween<
  Set,
  Start extends string,
  End extends string
> = Set extends `${Start}${infer _X}${End}` ? _X : never

/**
 * Union of all translation keys available
 */
export type TranslationKey = keyof typeof messages

/**
 * Union of all suffixes available for form.placeholder.
 */
export type TFieldPlaceHolder = FilterStartingWith<
  TranslationKey,
  'form.placeholder.'
>

/**
 * Union of all suffixes available to form.validation.
 */
export type TFieldError = FilterStartingWith<TranslationKey, 'form.validation.'>

/**
 * Union of all field names that have label form.field.${fieldName}.label
 */
export type TFieldLabel = FilterBetween<TranslationKey, 'form.field.', '.label'>