Cashify 💸

Lightweight currency conversion library, successor of money.js

• Motivation
• Highlights
• Install
• Usage
  • With constructor
  • Without constructor
  • Parsing
  • Integration with big.js
  • Integration with currency.js
• API
  • Cashify({base, rates})
    • base
    • rates
    • BigJs
  • convert(amount, {from, to, base, rates})
    • amount
    • from
    • to
    • base
    • rates
    • BigJs
  • parse(expression)
    • expression
• Migrating from money.js
• Floating point issues
• Related projects
• License

Motivation

This package was created, because the popular money.js library:

• is not maintained (last commit was ~5 years ago)
• has over 20 open issues
• does not support TypeScript
• has implicit globals
• does not have any unit tests
• has floating point issues

Highlights

• Simple API
• 0 dependencies
• Actively maintained
• Well tested and documented
• Easy migration from money.js
• Written in TypeScript
• ESM-only

Install

$ npm install cashify

Please note that starting with version 3.0.0 this package is ESM-only and thus requires Node.js v14 or higher.

Usage

With constructor

import {Cashify} from 'cashify';

const rates = {
	GBP: 0.92,
	EUR: 1.00,
	USD: 1.12
};

const cashify = new Cashify({base: 'EUR', rates});

const result = cashify.convert(10, {from: 'EUR', to: 'GBP'});

console.log(result); //=> 9.2

Without constructor

Using the Cashify constructor is not required. Instead, you can just use the convert function:

import {convert} from 'cashify';

const rates = {
	GBP: 0.92,
	EUR: 1.00,
	USD: 1.12
};

const result = convert(10, {from: 'EUR', to: 'GBP', base: 'EUR', rates});

console.log(result); //=> 9.2

Parsing

Cashify supports parsing, so you can pass a string to the amount argument and the from and/or to currency will be automatically detected:

import {Cashify} from 'cashify';

const rates = {
	GBP: 0.92,
	EUR: 1.00,
	USD: 1.12
};

const cashify = new Cashify({base: 'EUR', rates});

// Basic parsing
cashify.convert('€10 EUR', {to: 'GBP'});

// Full parsing
cashify.convert('10 EUR to GBP');

Alternatively, if you just want to parse a string without conversion you can use the parse function which returns an object with parsing results:

import {parse} from 'cashify';

parse('10 EUR to GBP'); //=> {amount: 10, from: 'EUR', to: 'GBP'}

Note: If you want to use full parsing, you need to pass a string in a specific format:

10 usd to pln
12.5 GBP in EUR
3.1415 eur as chf

You can use to, in or as to separate the expression (case insensitive). Used currencies name case doesn't matter, as cashify will automatically convert them to upper case.

Integration with big.js

big.js is a small JavaScript library for arbitrary-precision decimal arithmetic. You can use it with cashify to make sure you won't run into floating point issues:

import {Cashify} from 'cashify';
import Big from 'big.js';

const rates = {
	EUR: 0.8235,
	USD: 1
};

const cashify = new Cashify({base: 'USD', rates});

const result = cashify.convert(1, {
	from: 'USD',
	to: 'EUR',
	BigJs: Big
});

console.log(result); //=> 8.235 (without big.js you would get something like 0.8234999999999999)

Integration with currency.js

currency.js is a small and lightweight library for working with currency values. It integrates well with cashify. In the following example we are using it to format the conversion result:

import {Cashify} from 'cashify';
import currency from 'currency.js';

const rates = {
	GBP: 0.92,
	EUR: 1.00,
	USD: 1.12
};

const cashify = new Cashify({base: 'EUR', rates});

const converted = cashify.convert(8635619, {from: 'EUR', to: 'GBP'}); // => 7944769.48

// Format the conversion result
currency(converted, {symbol: '€', formatWithSymbol: true}).format(); // => €7,944,769.48

API

Cashify({base, rates, BigJs})

Constructor.

base

Type: string

The base currency.

rates

Type: object

An object containing currency rates (for example from an API, such as Open Exchange Rates).

BigJs

Type: big.js constructor

See integration with big.js.

convert(amount, {from, to, base, rates}) with and without constructor

Returns conversion result (number).

amount

Type: number or string

Amount of money you want to convert. You can either use a number or a string. If you choose the second option, you can take advantage of parsing and not specify from and/or to argument(s).

from

Type: string

Currency from which you want to convert. You might not need to specify it if you are using parsing.

to

Type: string

Currency to which you want to convert. You might not need to specify it if you are using parsing.

base

Type: string

The base currency.

rates

Type: object

An object containing currency rates (for example from an API, such as Open Exchange Rates).

BigJs

Type: big.js constructor

See integration with big.js.

parse(expression)

Returns an object, which contains parsing results:

{
	amount: number;
	from: string | undefined;
	to: string | undefined;
}

expression

Type: string

Expression you want to parse, ex. 10 usd to pln or €1.23 eur

Migrating from money.js

With Cashify constructor:

- import fx from 'money';
+ import {Cashify} from 'cashify';

- fx.base = 'EUR';
- fx.rates = {
-	GBP: 0.92,
-	EUR: 1.00,
-	USD: 1.12
- };

+ const rates = {
+	 GBP: 0.92,
+	 EUR: 1.00,
+	 USD: 1.12
+ };

+ const cashify = new Cashify({base: 'EUR', rates});

- fx.convert(10, {from: 'GBP', to: 'EUR'});
+ cashify.convert(10, {from: 'GBP', to: 'EUR'});

With convert function:

- import fx from 'money';
+ import {convert} from 'cashify';

- fx.base = 'EUR';
- fx.rates = {
-	GBP: 0.92,
-	EUR: 1.00,
-	USD: 1.12
- };

+ const rates = {
+	 GBP: 0.92,
+	 EUR: 1.00,
+	 USD: 1.12
+ };

- fx.convert(10, {from: 'GBP', to: 'EUR'});
+ convert(10, {from: 'GBP', to: 'EUR', base: 'EUR', rates});

Floating point issues

When working with currencies, decimals only need to be precise up to the smallest cent value while avoiding common floating point errors when performing basic arithmetic.

Let's take a look at the following example:

import fx from 'money';
import {Cashify} from 'cashify';

const rates = {
	GBP: 0.92,
	USD: 1.12
};

fx.rates = rates;
fx.base = 'EUR';

const cashify = new Cashify({base: 'EUR', rates});

fx.convert(10, {from: 'EUR', to: 'GBP'}); //=> 9.200000000000001
cashify.convert(10, {from: 'EUR', to: 'GBP'}); //=> 9.2

As you can see, money.js doesn't handle currencies correctly and therefore a floating point issues are occuring. Even though there's just a minor discrepancy between the results, if you're converting large amounts, that can add up.

Cashify solves this problem the same way as currency.js - by working with integers behind the scenes. This should be okay for most reasonable values of currencies; if you want to avoid all floating point issues, see integration with big.js.

Related projects

• nestjs-cashify - Node.js Cashify module for Nest.js.
• cashify-rs - Cashify port for Rust.

License

MIT © Antoni Kępiński