react-currency-input-field/src/components/utils/getLocaleConfig.ts

React <input/> component for formatting currency and numbers.

import { IntlConfig } from '../CurrencyInputProps';

type LocaleConfig = {
  currencySymbol: string;
  groupSeparator: string;
  decimalSeparator: string;
  prefix: string;
  suffix: string;
};

const defaultConfig: LocaleConfig = {
  currencySymbol: '',
  groupSeparator: '',
  decimalSeparator: '',
  prefix: '',
  suffix: '',
};

/**
 * Get locale config from input or default
 */
export const getLocaleConfig = (intlConfig?: IntlConfig): LocaleConfig => {
  const { locale, currency, ...formatOptions } = intlConfig || {};
  const numberFormatter = locale
    ? new Intl.NumberFormat(locale, {
        ...formatOptions,
        ...(currency && { currency, style: 'currency' }),
      })
    : new Intl.NumberFormat();

  return numberFormatter.formatToParts(1000.1).reduce((prev, curr, i): LocaleConfig => {
    if (curr.type === 'currency') {
      if (i === 0) {
        return { ...prev, currencySymbol: curr.value, prefix: curr.value };
      } else {
        return { ...prev, currencySymbol: curr.value, suffix: curr.value };
      }
    }
    if (curr.type === 'group') {
      return { ...prev, groupSeparator: curr.value };
    }
    if (curr.type === 'decimal') {
      return { ...prev, decimalSeparator: curr.value };
    }

    return prev;
  }, defaultConfig);
};