@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

1npm 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.

Usage

First we need to import the library.

1import { Money, Currencies } from '@screeny05/ts-money'

or in javascript:

1const TsMoney = require('@screeny05/ts-money')
2const Money = TsMoney.Money
3const 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.

1const fiveEur = new Money(500, Currencies.EUR)
2const tenDollars = Money.fromInteger({ amount: 1000, currency: Currencies.USD })
3const someDollars = Money.fromDecimal(15.25, 'USD')
4
5// the following will fail and throw an Error since USD allows for 2 decimals
6const moreDollars = Money.fromDecimal(15.3456, Currencies.USD)
7// but with rounder function provider the following will work
8const someMoreDollars = Money.fromDecimal(15.12345, 'USD', Math.ceil)

The Currency interface hold the following properties:

1interface Currency {
2  decimal_digits: number
3  code: string
4}

Ex:

1import { Currency } from '@screeny05/ts-money'
2
3const usd: Currency = {
4  decimal_digits: 2,
5  code: 'USD',
6}

Basic arithmetics

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

1const fiveEur = new Money(500, Currencies.EUR) // 5 EUR
2
3// add
4fiveEur.add(new Money(250, Currencies.EUR)) // 7.50 EUR
5
6// subtract
7fiveEur.subtract(new Money(470, Currencies.EUR)) // 0.30 EUR
8
9// multiply
10fiveEur.multiply(1.2345) // 6.17 EUR
11fiveEur.multiply(1.2345, Math.ceil) // 6.18 EUR
12
13// divide
14fiveEur.divide(2.3456) // 2.13 EUR
15fiveEur.divide(2.3456, Math.ceil) // 2.14 EUR
16
17// fraction calculation
18fiveEur.fractionOf(new Money(750, Currencies.EUR)) // 0.6667
19
20// percentage calculation (same as fraction but with rounding and precision)
21fiveEur.percentageOf(new Money(750, Currencies.EUR)) // 67
22fiveEur.percentageOf(new Money(750, Currencies.EUR), 2) // 66.67
23fiveEur.percentageOf(new Money(750, Currencies.EUR), 2, 'floor') // 66.66

Allocating funds

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

1const tenEur = new Money(1000, Currencies.EUR)
2
3// divide 10 EUR into 3 parts
4const shares = tenEur.allocate([1, 1, 1])
5// returns an array of Money instances worth [334,333,333]
6
7// split 5 EUR 70/30
8const fiveEur = new Money(500, Currencies.EUR)
9const shares = fiveEur.allocate([70, 30])
10// 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.

1const fiveEur = new Money(500, Currencies.EUR)
2const anotherFiveEur = new Money(500, Currencies.EUR)
3const sevenEur = new Money(700, Currencies.EUR)
4const fiveDollars = new Money(500, Currencies.USD)
5
6fiveEur.equals(fiveDollars) // return false
7fiveEur.equals(anotherFiveEur) // return true
8
9fiveEur.compare(sevenEur) // return -1
10sevenEur.compare(fiveEur) // return 1
11fiveEur.compare(anotherFiveEur) // return 0
12
13fiveEur.compare(fileDollars) // throw Error
14
15fiveEur.greaterThan(sevenEur) // return false
16fiveEur.greaterThanOrEqual(sevenEur) // return false
17fiveEur.lessThan(sevenEur) // return true
18fiveEur.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:

1import { Money, Currencies } from '@screeny05/ts-money'
2
3Currencies.LTC = {
4  decimal_digits: 8,
5  code: 'LTC',
6}
7
8const m1 = new Money(12, 'LTC')
9const m2 = new Money(234, Currencies.USD)
10const m3 = new Money(543, Currencies.LTC)

Case insensitive currencies

Money accepts currencies as case insensitive:

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

Development

Install dependencies

1npm install

Build library

1npm run build

Run tests

1npm test

License

The MIT License