i18n-wrapper.ts

const IntlMessageFormat = require('intl-messageformat');

var globalLocale: string = '';

export function getI18n({ messages }: I18nOptions): I18n {
  return {
    messages: () => getMessages(messages(globalLocale))
  };
}

function getMessages(messages: Dictionary<string>): Dictionary<CallBackFunction> {
  const result: Dictionary<CallBackFunction> = {};

  Object.keys(messages).map((key: string) => {
    result[key] = function(values: Dictionary<string>) {
      const msg = new IntlMessageFormat(messages[key], globalLocale);
      return msg.format(values);
    };
  });

  return result;
}

export function setGlobalLocale(options: GlobalLocale) {
  globalLocale = options.locale;
}

interface GlobalLocale {
  locale: string;
}

interface I18n {
  messages(): Dictionary<CallBackFunction>;
}

interface I18nOptions {
  messages(locale: string): Dictionary<string>;
}

interface CallBackFunction {
  (values: Dictionary<string>): void
}

interface Dictionary<T> {
  [key: string]: T;
}

Usage.md

Prepare

Create directory locale. Create 3 files below.

index.ts

import { getI18n } from '../i18n';

export const i18n = getI18n({
  messages: locale => require(`./locale.${locale}.json`)
});

locale.en.json

{
  "greeting": "Hello",
  "lol": "hello {someone}. My name is {myName}"
}

locale.vi.json

{
  "greeting": "Xin chao",
  "lol": "chao {someone}. Ten toi la {myName}"
}

main app

import { setGlobalLocale } from 'i18n-wrapper';
import { i18n } from './locale';

setGlobalLocale({ locale: 'en' });
const { lol } = i18n.messages();
const lolContent = lol({ someone: 'John', myName: 'David' });
console.log(lolContent);