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1.1.3 • Public • Published

Exchange Number Formatting (ExchNumberFormat)

ExchNumberFormat is a comprehensive and customizable number formatting utility, designed specifically for financial and cryptocurrency applications. It extends the standard Intl.NumberFormat functionality with support for custom currencies, including cryptocurrencies, and provides additional formatting options.


  • Standard and Custom Currencies: Extensive support for both standard ISO currencies and custom-defined currencies including cryptocurrencies.
  • Rounding Modes: Supports various rounding modes to meet different financial calculations requirements.
  • Locale-Aware Formatting: Offers locale-aware formatting, supporting different number styles and notations.
  • Custom Currency Attributes: Manages custom attributes for each currency, such as symbols, codes, and decimal places.
  • Dynamic Currency Support: Dynamically adds or modifies currency definitions at runtime using useCustomCurrency and customCurrency options.


Install the package using npm:

npm i exchange-rounding

Or using yarn:

yarn add exchange-rounding


Basic Usage

import ExchNumberFormat from 'exchange-rounding';

// Example: Formatting a number with Bitcoin currency
const bitcoinFormatter = new ExchNumberFormat('en-US', {
    style: 'currency',
    currency: 'BTC',
    roundingMode: 'halfFloor',
    currencyDisplay: 'symbol'

const formattedBTC = bitcoinFormatter.format(1234.567);
console.log(formattedBTC); // Output: '₿1,234.567'

// Example: Formatting with custom options
const customFormatter = new ExchNumberFormat('en-US', {
    style: 'decimal',
    minimumFractionDigits: 2,
    maximumFractionDigits: 5

const formattedNumber = customFormatter.format(1234.56789);
console.log(formattedNumber); // Output: '1,234.56789'

Advanced Usage with Custom Currencies

const customCurrencyData = {
    'XCB': {
        symbol: '₡',
        narrowSymbol: '₡',
        code: 'XCB',
        name: 'CoreCoin',
        defaultDecimals: 2

const formatter = new ExchNumberFormat('en-US', {
    useCustomCurrency: true,
    customCurrency: customCurrencyData,
    currency: 'XCB'

console.log(formatter.format(1234.567)); // Outputs: '₡1,234.57'

API Reference

new ExchNumberFormat(locales, options)

Creates a new formatter instance configured with the specified locales and options.


  • locales: A string with a BCP 47 language tag, or an array of such strings.
  • options: Configuration options for the formatter.


  • Inherits all options from Intl.NumberFormatOptions.
  • useAliases: Enables the use of currency aliases.
  • aliases: Defines mappings from alias strings to standard currency codes.
  • useCustomCurrency: Enables the use of a custom currency dictionary.
  • customCurrency: Specifies custom currency settings.
  • wrapped: Indicates if the currency symbol should be wrapped with custom characters.
  • wrappedSymbol: The symbol used to wrap the currency symbol.
  • digitized: Indicates if the numeric values should be displayed with digital symbols.
  • digitizedSymbol: The symbol used to represent digitized values.
  • roundingMode: The rounding mode to use when formatting numbers.

Rounding Modes

  • ceil: Rounds numbers up.
  • floor: Rounds numbers down.
  • expand: Similar to ceil but expands beyond the typical rounding limits.
  • trunc: Truncates the number without rounding.
  • halfCeil: Rounds half values up.
  • halfFloor: Rounds half values down.
  • halfExpand: Expands half values during rounding.
  • halfTrunc: Truncates half values.
  • halfEven: Rounds half values to the nearest even number.


Formats a number according to the instance's locale and formatting options.


Returns an array of objects representing the number string in parts that can be used for custom formatting.


Checks if the specified currency is supported by the formatter. Returns true if the currency is supported, false otherwise. If the formatter failed, an error is thrown.


Prints the version of the exchange-rounding package.


Contributions are welcome! Feel free to open an issue or submit a pull request on our GitHub repository.


This project is licensed under the CORE License.

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