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Format Currency

formatCurrency​

The formatCurrency function formats a number or numeric string as a locale-aware currency string, automatically handling symbol placement, decimal separators, and grouping. It uses the browser's built-in Intl.NumberFormat API for accurate localization.

Function Signature​

function formatCurrency( value: Numeric,  currency?: CurrencyCode,  locale?: LocaleCode ): string;

Parameters​

  • value (Numeric): The number or numeric string to format (e.g., 42 or "42.50").
  • currency (optional, CurrencyCode): ISO 4217 currency code (default: 'USD').
  • locale (optional, LocaleCode): BCP 47 locale code (default: auto-detected based on currency).

Types​

Numeric​

Union type accepting numbers or numeric strings:

type Numeric = number | `${number}`;

CurrencyCode​

All supported ISO 4217 currency codes (e.g., 'USD', 'EUR', 'JPY'):

type CurrencyCode = keyof typeof CURRENCY_LOCALES | (typeof CURRENCY_CODES)[number];

LocaleCode​

Supported BCP 47 locale codes (e.g., 'en-US', 'fr-FR', 'ja-JP'):

type LocaleCode = (typeof CURRENCY_LOCALES)[keyof typeof CURRENCY_LOCALES] | (typeof LOCALE_CODES)[number];

Return Value​

Returns a formatted currency string with:

  • Localized symbol/number placement
  • Correct decimal/grouping separators
  • Currency symbol or code

Example Usage​

Basic Usage (USD Default)​

import { formatCurrency } from 'nhb-toolbox';

console.log(formatCurrency(1234.56)); // "$1,234.56" (en-US locale)

Specific Currency​

console.log(formatCurrency(99.99, 'EUR')); // "99,99 €"
console.log(formatCurrency("5000", 'JPY')); // "￥5,000" (ja-JP locale)
console.log(formatCurrency("5000", 'BDT')); // "৫,০০০.০০৳" (bn-BD locale)

Custom Locale Override​

console.log(formatCurrency(1500, 'EUR', 'fr-FR')); // "1 500,00 €" 
console.log(formatCurrency(1500, 'EUR', 'de-DE')); // "1.500,00 €"
console.log(formatCurrency(1500, 'BDT', 'en-US')); // "BDT 1,500.00"

Notes​

  • Automatic Locale Detection: If no locale is provided, uses CURRENCY_LOCALES mapping (e.g., USD → en-US, EUR → de-DE).
  • Negative Values: Formats negative numbers according to locale (e.g., -42 → -$42.00 or ($42.00)).
  • Numeric Strings: Accepts strings like "42.5" (converted to numbers internally).
  • Browser Support: Relies on Intl.NumberFormat (supported in all modern browsers).

Supported Currencies & Locales​

Full lists are available in the package as:

  • CURRENCY_CODES: Array of all ISO 4217 currency codes
  • LOCALE_CODES: Array of all BCP 47 locale codes
  • CURRENCY_LOCALES: Mapping of currencies to their default locales

Aliases​

  • convertNumberToCurrency: Alias for formatCurrency.

Conclusion​

formatCurrency provides robust international currency formatting with minimal configuration, ideal for e-commerce, financial apps, and multi-regional dashboards. The extensive currency/locale support ensures accurate formatting for global audiences.