@screeny05/ts-money

TS Money is a Typescript port of the great js-money package, which is an implementation of Martin Fowlers Money pattern.

Install

npm install @screeny05/ts-money

Differences from original ts-money

• Currencies are now exported in a standalone object.
• Fixed bug with allocate method when a single allocation is zero. (thanks to @dotpack, see PR #5)
• Drastically reduced bundle-size by getting rid of lodash and removing unnecessary currency-data.
  • Instead of using currency-data like currency-name, symbols, etc. from this package you should rely on either your environments Intl.DisplayNames API or the currency-codes package.
• Added Money.from(amount: Amount) as shortcut for Money.fromInteger(amount: Amount)
• Added Money#fractionOf() and Money#percentageOf() (see below)
• Migrated package to vitest and unbuild.
• Throws a more descriptive error when dividing by zero.

Usage

First we need to import the library.

import { Money, Currencies } from '@screeny05/ts-money'

or in javascript:

const TsMoney = require('@screeny05/ts-money')
const Money = TsMoney.Money
const Currencies = TsMoney.Currencies

Creating a new instance

There are multiple options of what to pass into the constructor to create a new Money instance:

• amount as number, currency as string
• amount as number, currency as object
• object with amount and currency fields (only with fromInteger and fromDecimal methods)

Amounts can be supplied either as integers or decimal numbers.

Instances of Money are immutable and each arithmetic operation will return a new instance of the object.

When using decimals the library will allow only decimals with the precision allowed by the currencies smallest unit.

const fiveEur = new Money(500, Currencies.EUR)
const tenDollars = Money.fromInteger({ amount: 1000, currency: Currencies.USD })
const someDollars = Money.fromDecimal(15.25, 'USD')

// the following will fail and throw an Error since USD allows for 2 decimals
const moreDollars = Money.fromDecimal(15.3456, Currencies.USD)
// but with rounder function provider the following will work
const someMoreDollars = Money.fromDecimal(15.12345, 'USD', Math.ceil)

The Currency interface hold the following properties:

interface Currency {
  decimal_digits: number
  code: string
}

Ex:

import { Currency } from '@screeny05/ts-money'

const usd: Currency = {
  decimal_digits: 2,
  code: 'USD',
}

Basic arithmetics

Arithmetic operations involving multiple objects are only possible on instances with the same currency and will throw an Error otherwise.

const fiveEur = new Money(500, Currencies.EUR) // 5 EUR

// add
fiveEur.add(new Money(250, Currencies.EUR)) // 7.50 EUR

// subtract
fiveEur.subtract(new Money(470, Currencies.EUR)) // 0.30 EUR

// multiply
fiveEur.multiply(1.2345) // 6.17 EUR
fiveEur.multiply(1.2345, Math.ceil) // 6.18 EUR

// divide
fiveEur.divide(2.3456) // 2.13 EUR
fiveEur.divide(2.3456, Math.ceil) // 2.14 EUR

// fraction calculation
fiveEur.fractionOf(new Money(750, Currencies.EUR)) // 0.6667

// percentage calculation (same as fraction but with rounding and precision)
fiveEur.percentageOf(new Money(750, Currencies.EUR)) // 67
fiveEur.percentageOf(new Money(750, Currencies.EUR), 2) // 66.67
fiveEur.percentageOf(new Money(750, Currencies.EUR), 2, 'floor') // 66.66

Allocating funds

Will divide the funds based on the ratio without losing any pennies.

const tenEur = new Money(1000, Currencies.EUR)

// divide 10 EUR into 3 parts
const shares = tenEur.allocate([1, 1, 1])
// returns an array of Money instances worth [334,333,333]

// split 5 EUR 70/30
const fiveEur = new Money(500, Currencies.EUR)
const shares = fiveEur.allocate([70, 30])
// returns an array of money [350,150]

Comparison and equality

Two objects are equal when they are of the same amount and currency. Trying to compare 2 objects with different currencies will throw an Error.

const fiveEur = new Money(500, Currencies.EUR)
const anotherFiveEur = new Money(500, Currencies.EUR)
const sevenEur = new Money(700, Currencies.EUR)
const fiveDollars = new Money(500, Currencies.USD)

fiveEur.equals(fiveDollars) // return false
fiveEur.equals(anotherFiveEur) // return true

fiveEur.compare(sevenEur) // return -1
sevenEur.compare(fiveEur) // return 1
fiveEur.compare(anotherFiveEur) // return 0

fiveEur.compare(fileDollars) // throw Error

fiveEur.greaterThan(sevenEur) // return false
fiveEur.greaterThanOrEqual(sevenEur) // return false
fiveEur.lessThan(sevenEur) // return true
fiveEur.lessThanOrEqual(fiveEur) // return true

Modifications

Some changes have been made compared with the javascript version:

Currencies object

Currencies are now exported in a standalone object:

import { Money, Currencies } from '@screeny05/ts-money'

Currencies.LTC = {
  decimal_digits: 8,
  code: 'LTC',
}

const m1 = new Money(12, 'LTC')
const m2 = new Money(234, Currencies.USD)
const m3 = new Money(543, Currencies.LTC)

Case insensitive currencies

Money accepts currencies as case insensitive:

const m1 = new Money(1, 'usd')
const m2 = new Money(2, 'USD')
const m3 = new Money(3, 'Usd')

Development

Install dependencies

npm install

Build library

npm run build

Run tests

npm test

License

The MIT License