locale-decimal-parser

Locale-aware utility for parsing and formatting decimal numbers.
Handles thousands and decimal separators automatically based on the user's or a given locale — ideal for forms, reports, and financial data.

Features

• Parse localized user input like "1.234,56" or "1,234.56" reliably
• Format numbers into any locale (Intl.NumberFormat)
• Supports manual locale override
• TypeScript-first

Installation

npm install locale-decimal-parser
# or
yarn add locale-decimal-parser

Usage

import { parseLocalizedDecimal, formatDecimalToLocale } from 'locale-decimal-parser';

// Parsing
parseLocalizedDecimal('1.234,56', 'de-DE'); // => 1234.56
parseLocalizedDecimal('1,234.56', 'en-US'); // => 1234.56
parseLocalizedDecimal('.75', 'en-US');      // => 0.75
parseLocalizedDecimal(',75', 'de-DE');      // => 0.75

// Formatting
formatDecimalToLocale(1234.56, 'de-DE');    // => '1.234,56'
formatDecimalToLocale(1234.56, 'en-US');    // => '1,234.56'

// With formatting options
formatDecimalToLocale(1234.56, 'en-US', {
  style: 'currency',
  currency: 'USD',
}); // => '$1,234.56'

Note on Locale Support

Currently tested and verified with:

• de-DE (German)
• en-US (American English)

Support for other locales may vary depending on the browser's implementation of Intl and formatting behavior. Contributions are welcome!

API Reference

parseLocalizedDecimal

parseLocalizedDecimal(input: string, locale?: string): number | null

Parses a localized decimal string and returns a number or null if the input is invalid.

Parameters

• input: The user-entered number as a string, e.g., "1.234,56".
• locale (optional): A locale string (e.g., "de-DE"). Defaults to the user's browser locale.

Returns

• A number if parsing was successful
• null if the input could not be parsed

Example

parseLocalizedDecimal('1.234,56', 'de-DE'); // 1234.56
parseLocalizedDecimal('1,234.56', 'en-US'); // 1234.56
parseLocalizedDecimal('invalid');           // null

formatDecimalToLocale

formatDecimalToLocale(value: number, locale?: string, options?: Intl.NumberFormatOptions): string

Formats a number into a localized string using Intl.NumberFormat.

Parameters

• value: The number to format.
• locale (optional): A locale string (e.g., "en-US"). Defaults to the user's browser locale.
• options (optional): An object following Intl.NumberFormatOptions.

Returns

• A localized string representation of the number

Example

formatDecimalToLocale(1234.56, 'de-DE'); // "1.234,56"
formatDecimalToLocale(1234.56, 'en-US'); // "1,234.56"

formatDecimalToLocale(1234.56, 'en-US', {
  style: 'currency',
  currency: 'USD',
}); // "$1,234.56"

License

MIT