parseQuantity

Parses a quantity string into its numeric value

Usage

Parse a quantity string like "2 dollars" into its numeric value. You must provide a unit conversion map, with optional short unit aliases.

import * as _ from 'radashi'

const moneyUnits = {
  units: {
    cent: 1,
    dollar: 100,
  },
  short: {
    $: 'dollar',
  },
} as const

_.parseQuantity('1 cent', moneyUnits)
// => 1

_.parseQuantity('2 dollars', moneyUnits)
// => 200

_.parseQuantity('5$', moneyUnits)
// => 500

You may use the QuantityParser class instead, which is more efficient for repeated parsing.

const moneyParser = new _.QuantityParser(moneyUnits)

If you specifically need to parse a duration (e.g. “1 hour”, “2 seconds”) into milliseconds, you can use the parseDuration function instead.

Subclassing

You can subclass QuantityParser to create a parser for a specific unit.

import { QuantityParser, type QuantityString } from 'radashi'

export type DistanceUnit = keyof typeof DistanceParser.units
export type DistanceShortUnit = keyof typeof DistanceParser.shortUnits

export type DistanceString = QuantityString<DistanceUnit, DistanceShortUnit>

export class DistanceParser extends QuantityParser<DistanceUnit, DistanceShortUnit> {
  constructor() {
    super({
      units: DistanceParser.units,
      short: DistanceParser.shortUnits,
    })
  }

  static units = {
    kilometer: 1_000,
    mile: 1_852,
    yard: 0.9144,
    foot: 0.3048,
    meter: 1,
  } as const

  static shortUnits = {
    km: 'kilometer',
    mi: 'mile',
    yd: 'yard',
    ft: 'foot',
    m: 'meter',
  } as const
})

// Usage
const distanceParser = new DistanceParser()

distanceParser.parse('1 kilometer') // => 1_000
distanceParser.parse('1km') // => 1_000
distanceParser.parse('1 mile') // => 1_852
distanceParser.parse('1mi') // => 1_852
distanceParser.parse('1 yard') // => 0.9144
distanceParser.parse('1yd') // => 0.9144
distanceParser.parse('1 foot') // => 0.3048
distanceParser.parse('1ft') // => 0.3048
distanceParser.parse('1 meter') // => 1

You may want to create a wrapper function to make it easier to use.

import { DistanceParser, type DistanceString } from './DistanceParser'

const parser = new DistanceParser()

export function parseDistance(input: DistanceString): number {
  return parser.parse(input)
}

// Usage
parseDistance('1 kilometer') // => 1_000
parseDistance('1km') // => 1_000
parseDistance('1 mile') // => 1_852