Like _.mapValues, but asynchronous

mapValuesAsync.ts

// https://gist.github.com/eschwartz/70a15f12e6ef90f377d5d51fba9c86d8
import mapAsync from './mapAsync';

interface Dict<TVal> {
  [key: string]: TVal
}

async function mapValuesAsync<TVal, TRes>(obj:Dict<TVal>, iter:(val:TVal, key:string) => Promise<TRes>):Promise<Dict<TRes>> {
  const keyResPairs:[string, TRes][] = await mapAsync<string, [string, TRes]>(Object.keys(obj),
    async (key:string) => {
      const res = await iter(obj[key], key);
      return [key, res];
    }
  );

  return keyResPairs.reduce((obj:Dict<TRes>, [key, res]:[string, TRes]) => ({
    ...obj,
    [key]: res
  }), {});
}
export default mapValuesAsync;