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0.6.3 • Public • Published

JS Money

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JS Money is a JavaScript implementation of Martin Fowlers Money pattern.


The package is available through npm and bower.

$ npm install js-money
$ bower install js-money


First we need to import the library.

var Money = require('js-money');

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.

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

The currency object hold the following properties

        "symbol": "$",
        "name": "US Dollar",
        "symbol_native": "$",
        "decimal_digits": 2,
        "rounding": 0,
        "code": "USD",
        "name_plural": "US dollars"

Basic arithmetics

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

var fiveEur = new Money(500, Money.EUR); // 5 EUR
// add
fiveEur.add(new Money(250, Money.EUR)); // 7.50 EUR
// subtract 
fiveEur.subtract(new Money(470, Money.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

Allocating funds

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

var tenEur = new Money(1000, Money.EUR);
// divide 10 EUR into 3 parts
var shares = tenEur.allocate([1,1,1]); 
// returns an array of Money instances worth [334,333,333]
// split 5 EUR 70/30
var fiveEur = new Money(500, Money.EUR);
var 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.

var fiveEur = new Money(500, Money.EUR);
var anotherFiveEur = new Money(500, Money.EUR);
var sevenEur = new Money(700, Money.EUR);
var fiveDollars = new Money(500, Money.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


$ npm install
$ npm test


The MIT License

Copyright (c) 2014 David Kalosi http://davidkalosi.com/

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