NumberParser

A NumberParser can be used to perform locale-aware parsing of numbers from Unicode strings, as well as validation of partial user input. It automatically detects the numbering system used in the input, and supports parsing decimals, percentages, currency values, and units according to the locale.

Introduction#

Numbers can be formatted in many different ways, including percentages, units, decimals, currencies, and more. In addition, number formatting varies around the world. For example, currency symbols, units, decimal separators, and even digits themselves may be different across languages and regions. While Latin numerals are the most commonly used, many other numbering systems are also used around the world. For example, in the Latin numbering system, the number twelve is represented as “12”, and in the Arabic decimal system, it is “١٢”.

NumberParser is designed to validate and parse numbers from user input according to a specific locale and format. It supports several different numbering systems including the Latin, Arabic, and Han positional numbering systems, as well as parsing decimals, percentages, currencies, and unit values. The numbering system is automatically detected from the input string. This means that users may input numbers in a different numbering system than the default for their locale, e.g. a Latin number in an Arabic locale.

Parsing numbers while taking into account all locale-specific detail is quite complex and error-prone. NumberParser uses information about the locale and expected format for a number in order to parse it correctly. This means it is somewhat strict about the accepted formats. It is not designed to handle use cases where the user can enter numbers in an unknown format (e.g. either a unit value or a percentage), this must be known up front or selected via an external UI control.

Read our blog post for more details on how the number parser is implemented.

Example#

To create a NumberParser, call the constructor with a locale string and optional format options. The same options as supported by the Intl.NumberFormat object are supported. See the docs on MDN linked above for full details.

This example creates a parser than accepts values in inches in the en-US locale.

import {NumberParser} from '@internationalized/number';

let parser = new NumberParser('en-US', {style: 'unit', unit: 'inch'});
parser.parse('10 in'); // 10

import {NumberParser} from '@internationalized/number';

let parser = new NumberParser('en-US', {
  style: 'unit',
  unit: 'inch'
});
parser.parse('10 in'); // 10

import {NumberParser} from '@internationalized/number';

let parser =
  new NumberParser(
    'en-US',
    {
      style: 'unit',
      unit: 'inch'
    }
  );
parser.parse('10 in'); // 10

Interface#

Parsing#

Numbers can be parsed using the parse method. If the input is not a valid number according to the locale and format options, NaN is returned instead.

Decimals#

By default, or with the style: 'decimal' option, NumberParser supports parsing decimal values.

let parser = new NumberParser('en-US');
parser.parse('10.5'); // 10.5
parser.parse('-25.6'); // -25.6
parser.parse('1,000,000'); // 1000000
parser.parse('١٢'); // 12
parser.parse('X'); // NaN

let parser = new NumberParser('en-US');
parser.parse('10.5'); // 10.5
parser.parse('-25.6'); // -25.6
parser.parse('1,000,000'); // 1000000
parser.parse('١٢'); // 12
parser.parse('X'); // NaN

let parser =
  new NumberParser(
    'en-US'
  );
parser.parse('10.5'); // 10.5
parser.parse('-25.6'); // -25.6
parser.parse(
  '1,000,000'
); // 1000000
parser.parse('١٢'); // 12
parser.parse('X'); // NaN

Percentages#

The style: 'percent' option can be provided to the constructor to parse percentage values. In this mode, parsed values are divided by 100, for example the string "45%" is parsed as 0.45. The maximumFractionDigits option is also taken into account during parsing, and the resulting value is rounded accordingly.

let parser = new NumberParser('en-US', {
  style: 'percent',
  maximumFractionDigits: 2
});

parser.parse('45%'); // 0.45
parser.parse('62.3333%'); // 0.6233

let parser = new NumberParser('en-US', {
  style: 'percent',
  maximumFractionDigits: 2
});

parser.parse('45%'); // 0.45
parser.parse('62.3333%'); // 0.6233

let parser =
  new NumberParser(
    'en-US',
    {
      style: 'percent',
      maximumFractionDigits:
        2
    }
  );

parser.parse('45%'); // 0.45
parser.parse('62.3333%'); // 0.6233

Currency values#

The style: 'currency' option can be provided to the constructor to parse currency values. The currency option must also be passed to set the currency code (e.g. USD) to use. In addition, the currencyDisplay option can be used to choose whether to display the currency symbol, currency code, or currency name. Finally, the currencySign option can be set to accounting to use accounting notation for negative numbers, which uses parentheses rather than a minus sign in some locales.

Note that partial input is not accepted by this method. For example, if a partial currency symbol is included in the string, NaN will be returned. The isValidPartialNumber method, described below, can be used in scenarios where you have partial user input.

let parser = new NumberParser('en-US', {
  style: 'currency',
  currency: 'EUR',
  currencyDisplay: 'code',
  currencySign: 'accounting'
});

parser.parse('45'); // 45
parser.parse('EUR 45'); // 45
parser.parse('EUR 26.45'); // 26.45
parser.parse('EUR -25'); // -25
parser.parse('(EUR 25)'); // -25
parser.parse('EU 45'); // NaN (partial currency symbol)
parser.parse('$45'); // NaN (different currency symbol)

let parser = new NumberParser('en-US', {
  style: 'currency',
  currency: 'EUR',
  currencyDisplay: 'code',
  currencySign: 'accounting'
});

parser.parse('45'); // 45
parser.parse('EUR 45'); // 45
parser.parse('EUR 26.45'); // 26.45
parser.parse('EUR -25'); // -25
parser.parse('(EUR 25)'); // -25
parser.parse('EU 45'); // NaN (partial currency symbol)
parser.parse('$45'); // NaN (different currency symbol)

let parser =
  new NumberParser(
    'en-US',
    {
      style: 'currency',
      currency: 'EUR',
      currencyDisplay:
        'code',
      currencySign:
        'accounting'
    }
  );

parser.parse('45'); // 45
parser.parse('EUR 45'); // 45
parser.parse(
  'EUR 26.45'
); // 26.45
parser.parse('EUR -25'); // -25
parser.parse('(EUR 25)'); // -25
parser.parse('EU 45'); // NaN (partial currency symbol)
parser.parse('$45'); // NaN (different currency symbol)

Unit values#

The style: 'unit' option can be passed to the constructor to parse values with a unit of measurement. The unit option must also be passed to set which unit to use (e.g. inch). In addition, the unitDisplay option can be used to choose whether the unit is accepted in long, short, or narrow format.

let parser = new NumberParser('en-US', {
  style: 'unit',
  unit: 'inch',
  unitDisplay: 'long'
});

parser.parse('12'); // 12
parser.parse('12 inches'); // 12
parser.parse('1 inch'); // 1
parser.parse('12 in'); // NaN (partial unit)
parser.parse('23 ft'); // NaN (different unit)

let parser = new NumberParser('en-US', {
  style: 'unit',
  unit: 'inch',
  unitDisplay: 'long'
});

parser.parse('12'); // 12
parser.parse('12 inches'); // 12
parser.parse('1 inch'); // 1
parser.parse('12 in'); // NaN (partial unit)
parser.parse('23 ft'); // NaN (different unit)

let parser =
  new NumberParser(
    'en-US',
    {
      style: 'unit',
      unit: 'inch',
      unitDisplay: 'long'
    }
  );

parser.parse('12'); // 12
parser.parse(
  '12 inches'
); // 12
parser.parse('1 inch'); // 1
parser.parse('12 in'); // NaN (partial unit)
parser.parse('23 ft'); // NaN (different unit)

Validation#

NumberParser can also be used to validate partial user input using the isValidPartialNumber method, for example, as the user types into an input field. The parse method only accepts complete input, whereas isValidPartialNumber determines if the given input might be valid but incomplete. For example, only entering a decimal point is invalid when passed to parse, but accepted by isValidPartialNumber.

Note that partial units and currency symbols are not accepted. Since the unit itself must be known upfront and passed to the constructor, it is better to only allow entering a number rather and autocompleting the unit rather than typing it in one letter at a time.

let parser = new NumberParser('en-US', {style: 'unit', unit: 'inch'});
parser.isValidPartialNumber('.'); // true
parser.isValidPartialNumber('.2'); // true
parser.isValidPartialNumber('10 in'); // true
parser.isValidPartialNumber('10 i'); // false
parser.isValidPartialNumber('10 x'); // false

let parser = new NumberParser('en-US', {
  style: 'unit',
  unit: 'inch'
});
parser.isValidPartialNumber('.'); // true
parser.isValidPartialNumber('.2'); // true
parser.isValidPartialNumber('10 in'); // true
parser.isValidPartialNumber('10 i'); // false
parser.isValidPartialNumber('10 x'); // false

let parser =
  new NumberParser(
    'en-US',
    {
      style: 'unit',
      unit: 'inch'
    }
  );
parser
  .isValidPartialNumber(
    '.'
  ); // true
parser
  .isValidPartialNumber(
    '.2'
  ); // true
parser
  .isValidPartialNumber(
    '10 in'
  ); // true
parser
  .isValidPartialNumber(
    '10 i'
  ); // false
parser
  .isValidPartialNumber(
    '10 x'
  ); // false

Detecting the numbering system#

Under the hood, NumberParser automatically detects the numbering system used in the input. This is also exposed by the getNumberingSystem method, which returns a Unicode script identifier. For example, this can be used to create a number formatter based on the numbering system used in the input.

import {NumberFormatter, NumberParser} from '@internationalized/number';

let parser = new NumberParser('en-US', { style: 'decimal' });
let numberingSystem = parser.getNumberingSystem('١٢'); // -> 'arab'

let formatter = new NumberFormatter('en-US', {
  style: 'decimal',
  numberingSystem
});
formatter.format(12); // '١٢'

import {
  NumberFormatter,
  NumberParser
} from '@internationalized/number';

let parser = new NumberParser('en-US', {
  style: 'decimal'
});
let numberingSystem = parser.getNumberingSystem('١٢'); // -> 'arab'

let formatter = new NumberFormatter('en-US', {
  style: 'decimal',
  numberingSystem
});
formatter.format(12); // '١٢'

import {
  NumberFormatter,
  NumberParser
} from '@internationalized/number';

let parser =
  new NumberParser(
    'en-US',
    { style: 'decimal' }
  );
let numberingSystem =
  parser
    .getNumberingSystem(
      '١٢'
    ); // -> 'arab'

let formatter =
  new NumberFormatter(
    'en-US',
    {
      style: 'decimal',
      numberingSystem
    }
  );
formatter.format(12); // '١٢'