schummar-translate

TypeScript powered translation library for React and Node.js.

Example

Given a translation file like this:

// en.ts
export default {
  welcomeMessage: 'Hi, {name}',
  currentTime: 'It is now {time, time, short}',
} as const;

schummar-translate is able to provide type checking and autocomplete/IntelliSense for both translation keys and parameters in ICU format:

Getting started

Install schummar-translate.

npm install schummar-translate

Create and export a translator instance

// translate.ts
import { createTranslator, TranslationContextProvider } from 'schummar-translate/react';
import en from './en.ts';
import de from './de.ts';

export const { t, useTranslator, getTranslator } = createTranslator({
  sourceDictionary: en,
  sourceLocale: 'en',
  dicts: { de },
});

Use it everywhere in your app

import { t } from './translate';

export App() {
  const [locale, setLocale] = useState('en');

  const toggleLocale = () => {
    setLocale((locale) => (locale === 'en' ? 'de' : 'en'));
  }

  return (
    <TranslationContextProvider locale={locale}>
      <div onClick={toggleLocale}>
        {t('welcomeMessage', { name: 'schummar' })}
      </div>
    </TranslationContextProvider>
  )
}

API

createTranslator

function createTranslator(options: Options): ReturnValue;

type Options = {
  sourceDictionary?: { [id: string]: Dict | string };
  sourceLocale: string;
  fallbackLocale?: string | readonly string[] | ((locale: string) => string | readonly string[]);
  dicts?:
    | { [locale: string]: PartialDict<D> | (() => MaybePromise<PartialDict<D>>) }
    | ((locale: string) => MaybePromise<PartialDict<D> | null>);
  warn?: (locale: string, id: string) => void;
  fallback?: string | ((id: string, sourceTranslation: string) => string);
  placeholder?: string | ((id: string, sourceTranslation: string) => string);
  cacheOptions?: CacheOptions;
  dateTimeFormatOptions?: Intl.DateTimeFormatOptions;
  displayNamesOptions?: Intl.DisplayNamesOptions;
  listFormatOptions?: Intl.ListFormatOptions;
  numberFormatOptions?: Intl.NumberFormatOptions;
  pluralRulesOptions?: Intl.PluralRulesOptions;
  relativeTimeFormatOptions?: Intl.RelativeTimeFormatOptions;
};

type CacheOptions = {
  maxEntries?: number;
  ttl?: number;
};

type ReturnValue = {
  getTranslator: GetTranslator;
  useTranslator: UseTranslator;
  t: ReactTranslator;
  clearDicts: () => void;
};

The are two versions of this function, depending on the used import. When importing 'schummar-translate', it creates a translator without React support (and therefore without the dependency on React). Then the last three parameters do not apply and the return value only contains getTranslator. When importing 'schummar-translate/react' React support and the last three parameters are included.

• createTranslator creates and provides all the other functions and uses the passed in sourceDictionary to type them.
• sourceDictionary takes the source dictionary as seen above. If not provided, the dictionary for the source language will be loaded as any other. Also, if not provided, you will have to explicitly set the dictionary type: createTranslator<typeof mySourceDict>(...).
• sourceLocale is the locale of the source dictionary as ISO-639-1 code.
• fallbackLocale provides a locale that will be used as fallback if a translation key is not available for some locale.
• dicts provides all languages except the source language. It can either be an object with the locales as key and a dictionary or promise of a dictionary as value. Or it can be a function returning a dictionary or promise of a dictionary for a given locale. The last can be used to lazy load locales (expect source locale), for example with dynamic imports: dicts: (locale: string) => import(`./langs/${locale}`).then(mod => mod.default) or getting it from a cdn via fetch.
• warn lets you display warnings (e.g. to console.warn) when a translation key is missing in the active locale and no fallback is used.
• fallback lets you define you a static or dynamic string that will be displayed whenever a translation key is missing for the active locale.
• fallbackElement the same as fallback but also allows to pass a ReactNode to display more complex (e.g styled) fallbacks for translations embedded in JSX.
• placeholder lets you define a string that will be displayed in place of a translated string while the active locale is loading (when using promises)
• placeholderElement the same as placeholder but also allows to pass a ReactNode to display more complex (e.g styled) placeholders for translations embedded in JSX.
• cacheOptions.maxEntries the maximum amount of entries that are kept in cache. The cache is currently used to memoize Intl instances, since creating them is quite expensive.
• cacheOptions.ttl how long cache entries are kept, in milliseconds. Cleanup happens on next cache miss.
• dateTimeFormatOptions default options for dateTimeFormat calls.
• displayNamesOptions default options for dateTimeFormat calls.
• listFormatOptions default options for dateTimeFormat calls.
• numberFormatOptions default options for dateTimeFormat calls.
• pluralRulesOptions default options for dateTimeFormat calls.
• relativeTimeFormatOptions default options for dateTimeFormat calls.

The return value is meant to be exported so the provided functions can be used everywhere in your app: export const { getTranslator, useTranslator, t } = createTranslator({ ... })

t

function t(id: K, values: V, options?: Options): ReactNode;

type Options = {
  locale?: string;
  fallback?: React.ReactNode;
  placeholder?: React.ReactNode;
  component?: React.ElementType;
};

• locale allows to override the active locale. If not defined, the active locale is used as provided with TranslationContextProvider.
• fallback allows to override the fallback that was passed to createTranslator for just this instance.
• placeholder allows to override the placeholder that was passed to createTranslator for just this instance.
• component let's you define a component that will wrap the translated string. E.g. component: 'div' will result in <div>YOUR TEXT</div>

t can be used to translate string withing JSX: <div>{t('foo', { value: 42 })}</div>. id has to be a flattened key from the source dictionary. values has to be an object containing the ICU paramters used in the string in the source dictionary. If there are no parameters, values is optional.

Of course if you don't like the minimally named t you can rename it in the export: export const { getTranslator, useTranslator, t: translate } = ...

t.unknown

function t.unknown(id: string, values?: Record<string, unknown>, options?: Options): ReactNode;

type Options = {
  locale?: string;
  fallback?: React.ReactNode;
  placeholder?: React.ReactNode;
}

• locale allows to override the active locale. If not defined, the active locale is used as provided with TranslationContextProvider.
• fallback allows to override the fallback that was passed to createTranslator for just this instance.
• placeholder allows to override the placeholder that was passed to createTranslator for just this instance.

t.unknown does exactly the same as t but without type checking. This can be useful if if the translation is not necessarily available. E.g. t.unknown(`types.${currentType`, undefined, { fallback: currentType }).

t.format

function t.format(template: string, values: V): ReactNode;

t.format can be used to format something using ICU. E.g. t.format('{d, date, short}', { d: new Date() }).

t.render

function t.render(renderFn: (t: HookTranslator<D>) => ReactNode, dependencies?: any[]): ReactNode;

t.render can be used to get access to a translator instance as you would get from useTranslator. That is useful e.g. when working on a class component, where the hook is otherwise not available: <div>{t.render(t => <ComponentThatUsesStringProperty placeholder={t('key1')} />)}</div>

• renderFn will be executed to render
• dependencies if provided, will memoize the result of renderFn as long as dependencies stay the same (shallow compare) A common example will be to use the Intl api like: t.render(locale => new Intl.DateTimeFormat(locale).format(date), [date]).

t.locale

function f.locale: ReactNode;

t.locale returns the currently active locale. Mostly useful for useTranslator, to pass into another function.

t.{dateTimeFormat, displayNames, listFormat, numberFormat, pluralRules, relativeTimeFormat}

E.g.

function f.dateTimeFormat(date?: Date | number | string, options?: Intl.DateTimeFormatOptions): ReactNode;

t.dateTimeFormat formats dates and times. It proxies Intl.DateTimeFormat.format but adds caching and inject the active locale. The same is true for displayNames, listFormat, numberFormat, pluralRules and relativeTimeFormat. See MDN: Intl

useTranslator

function useTranslator(locale?: string): HookTranslator;

type HookTranslator = {
  (id: K, values: V, options?: Options): string | string[];
  unknow: (id: string, values?: Record<string, unknown>, options?: Options): string | string[];
  format: (template: string, values: V): string;
  locale: string;
}

type Options = {
  fallback?: string;
  placeholder?: string;
}

React hook that returns a translator that works very similarly to t, but being a hook itself, it does not need internal hooks and therefore returns a string instead of a ReactNode. That is useful in case you need to pass strings somewhere, e.g. as options to a select component etc. If the dictionary value is an array, an array of translated string will be returned. For more details see t, t.unknown and t.format.

getTranslator

function getTranslator(locale: string): Promise<Translator>;

type Translator = {
  (id: K, values: V, options?: Options): string | string[];
  unknow: (id: string, values?: Record<string, unknown>, options?: Options): string | string[];
  format: (template: string, values: V): string;
  locale: string;
}

type Options = {
  fallback?: string;
}

Returns a promise of a translator object. That method can be used in the backend or in the frontend outside of React components. It loads the necessary locales first then resolves the promise. The resulting translator is again very similar to t but obviously returning string and not ReactNode. If the dictionary value is an array, an array of translated string will be returned. For more details see t, t.unknown and t.format.

clearDicts

function clearDicts(): void;

Clears all dictionary and cache data. This will result in dictionaries being reloaded, as soon as they are used again. This allows loading new dictionary versions from a server, for example.