Plans: add support for client-side currency formatting

client/lib/format-currency/README.md

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+Format Currency
+==========
+Given a currency code, this library will take in a number and display it as money correctly.
+
+Usage
+==========
+```javascript
+import formatCurrency from 'lib/format-currency';
+
+const USD = formatCurrency( 9800900.32, 'USD' ); // '$9,800,900.32'
+const EUR = formatCurrency( 9800900.32, 'EUR' ); // '€9.800.900,32'
+const JPY = formatCurrency( 9800900.32, 'JPY' ); // '¥9,800,900'
+```
+
+Or
+
+```javascript
+import { getCurrencyObject } from 'lib/format-currency';
+const USD = getCurrencyObject( 9800900.32, 'USD' ); // { symbol: '$', integer: '9,800,900', fraction: '.32', sign: '' }
+
+```
+## Parameters
+
+### `number`
+
+<table>
+	<tr><th>Type</th><td>Number</td></tr>
+	<tr><th>Required</th><td>Yes</td></tr>
+</table>
+
+The number to format.
+
+### `code`
+
+<table>
+	<tr><th>Type</th><td>String</td></tr>
+	<tr><th>Required</th><td>Yes</td></tr>
+</table>
+
+The currency code to format with.
+
+## Option Properties
+
+### `symbol`
+
+<table>
+	<tr><th>Type</th><td>String</td></tr>
+	<tr><th>Required</th><td>No</td></tr>
+</table>
+
+Overrides the currency symbol. Eg replacing 'A$' instead of '$'
+
+### `decimal`
+
+<table>
+	<tr><th>Type</th><td>String</td></tr>
+	<tr><th>Required</th><td>No</td></tr>
+</table>
+
+Overrides the decimal mark. eg: 9.99 vs 9,99
+
+### `grouping`
+
+<table>
+	<tr><th>Type</th><td>String</td></tr>
+	<tr><th>Required</th><td>No</td></tr>
+</table>
+
+
+Overrides the thousands symbol grouping.
+
+### `precision`
+
+<table>
+	<tr><th>Type</th><td>Number</td></tr>
+	<tr><th>Required</th><td>No</td></tr>
+</table>
+
+The number of decimal places to display.

client/lib/format-currency/index.js

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+/**
+ * External dependencies
+ */
+import { numberFormat } from 'i18n-calypso';
+
+const CURRENCIES = {
+	USD: {
+		symbol: '$',
+		grouping: ',',
+		decimal: '.',
+		precision: 2
+	},
+	AUD: {
+		symbol: 'A$',
+		grouping: ',',
+		decimal: '.',
+		precision: 2
+	},
+	CAD: {
+		symbol: 'C$',
+		grouping: ',',
+		decimal: '.',
+		precision: 2
+	},
+	EUR: {
+		symbol: '€',
+		grouping: '.',
+		decimal: ',',
+		precision: 2
+	},
+	GBP: {
+		symbol: '£',
+		grouping: ',',
+		decimal: '.',
+		precision: 2
+	},
+	JPY: {
+		symbol: '¥',
+		grouping: ',',
+		decimal: '.',
+		precision: 0
+	}
+};
+
+/**
+ * Formats money with a given currency code
+ * @param   {Number}     number              number to format
+ * @param   {String}     code                currency code e.g. 'USD'
+ * @param   {Object}     options             options object
+ * @param   {String}     options.decimal     decimal symbol e.g. ','
+ * @param   {String}     options.grouping    thousands separator
+ * @param   {Number}     options.precision   decimal digits
+ * @param   {String}     options.symbol      currency symbol e.g. 'A$'
+ * @returns {?String}                        A formatted string.
+ */
+export default function formatCurrency( number, code, options = {} ) {
+	const currencyDefaults = getCurrencyDefaults( code );
+	if ( ! currencyDefaults || isNaN( number ) ) {
+		return null;
+	}
+	const {
+		decimal,
+		grouping,
+		precision,
+		symbol
+	} = { ...currencyDefaults, ...options };
+	const sign = number < 0 ? '-' : '';
+	const value = numberFormat( Math.abs( number ), {
+		decimals: precision,
+		thousandsSep: grouping,
+		decPoint: decimal
+	} );
+	return `${ sign }${ symbol }${ value }`;
+}
+
+/**
+ * Returns a formatted price object.
+ * @param   {Number}     number              number to format
+ * @param   {String}     code                currency code e.g. 'USD'
+ * @param   {Object}     options             options object
+ * @param   {String}     options.decimal     decimal symbol e.g. ','
+ * @param   {String}     options.grouping    thousands separator
+ * @param   {Number}     options.precision   decimal digits
+ * @param   {String}     options.symbol      currency symbol e.g. 'A$'
+ * @returns {?String}                        A formatted string e.g. { symbol:'$', integer: '$99', fraction: '.99', sign: '-' }
+ */
+export function getCurrencyObject( number, code, options = {} ) {
+	const currencyDefaults = getCurrencyDefaults( code );
+	if ( ! currencyDefaults || isNaN( number ) ) {
+		return null;
+	}
+	const {
+		decimal,
+		grouping,
+		precision,
+		symbol
+	} = { ...currencyDefaults, ...options };
+	const sign = number < 0 ? '-' : '';
+	const absNumber = Math.abs( number );
+	const rawInteger = Math.floor( absNumber );
+	const integer = numberFormat( rawInteger, {
+		decimals: 0,
+		thousandsSep: grouping,
+		decPoint: decimal
+	} );
+	const fraction = precision > 0
+		? numberFormat( absNumber - rawInteger, {
+			decimals: precision,
+			thousandsSep: grouping,
+			decPoint: decimal
+		} ).slice( 1 )
+		: '';
+	return {
+		sign,
+		symbol,
+		integer,
+		fraction
+	};
+}
+
+/**
+ * Returns currency defaults.
+ * @param   {String} code      currency code
+ * @returns {?Object}          currency defaults
+ */
+export function getCurrencyDefaults( code ) {
+	return CURRENCIES[ code ] || null;
+}

client/lib/format-currency/test/index.js

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+/**
+ * External dependencies
+ */
+import { expect } from 'chai';
+
+/**
+ * Internal dependencies
+ */
+import formatCurrency, { getCurrencyDefaults, getCurrencyObject } from 'lib/format-currency';
+
+describe( 'formatCurrency', () => {
+	it( 'formats a number to localized currency', () => {
+		const money = formatCurrency( 99.32, 'USD' );
+		expect( money ).to.equal( '$99.32' );
+	} );
+	it( 'adds a localized thousands separator', () => {
+		const money = formatCurrency( 9800900.32, 'USD' );
+		expect( money ).to.equal( '$9,800,900.32' );
+	} );
+	it( 'handles zero', () => {
+		const money = formatCurrency( 0, 'USD' );
+		expect( money ).to.equal( '$0.00' );
+	} );
+	it( 'handles negative values', () => {
+		const money = formatCurrency( -1234.56789, 'USD' );
+		expect( money ).to.equal( '-$1,234.57' );
+	} );
+	it( 'unknown currency codes return null', () => {
+		const money = formatCurrency( 9800900.32, {} );
+		expect( money ).to.equal( null );
+	} );
+
+	describe( 'supported currencies', () => {
+		it( 'USD', () => {
+			const money = formatCurrency( 9800900.32, 'USD' );
+			expect( money ).to.equal( '$9,800,900.32' );
+		} );
+		it( 'AUD', () => {
+			const money = formatCurrency( 9800900.32, 'AUD' );
+			expect( money ).to.equal( 'A$9,800,900.32' );
+		} );
+		it( 'CAD', () => {
+			const money = formatCurrency( 9800900.32, 'CAD' );
+			expect( money ).to.equal( 'C$9,800,900.32' );
+		} );
+		it( 'EUR', () => {
+			const money = formatCurrency( 9800900.32, 'EUR' );
+			expect( money ).to.equal( '€9.800.900,32' );
+		} );
+		it( 'GBP', () => {
+			const money = formatCurrency( 9800900.32, 'GBP' );
+			expect( money ).to.equal( '£9,800,900.32' );
+		} );
+		it( 'JPY', () => {
+			const money = formatCurrency( 9800900.32, 'JPY' );
+			expect( money ).to.equal( '¥9,800,900' );
+		} );
+	} );
+
+	describe( 'getCurrencyDefaults()', () => {
+		it( 'returns currency defaults', () => {
+			const audDefaults = getCurrencyDefaults( 'AUD' );
+			expect( audDefaults ).to.eql( {
+				symbol: 'A$',
+				grouping: ',',
+				decimal: '.',
+				precision: 2
+			} );
+		} );
+	} );
+
+	describe( 'getCurrencyObject()', () => {
+		it( 'handles zero', () => {
+			const money = getCurrencyObject( 0, 'USD' );
+			expect( money ).to.eql( {
+				symbol: '$',
+				integer: '0',
+				fraction: '.00',
+				sign: ''
+			} );
+		} );
+		it( 'handles negative values', () => {
+			const money = getCurrencyObject( -1234.56789, 'USD' );
+			expect( money ).to.eql( {
+				symbol: '$',
+				integer: '1,234',
+				fraction: '.57',
+				sign: '-'
+			} );
+		} );
+		describe( 'supported currencies', () => {
+			it( 'USD', () => {
+				const money = getCurrencyObject( 9800900.32, 'USD' );
+				expect( money ).to.eql( {
+					symbol: '$',
+					integer: '9,800,900',
+					fraction: '.32',
+					sign: ''
+				} );
+			} );
+			it( 'AUD', () => {
+				const money = getCurrencyObject( 9800900.32, 'AUD' );
+				expect( money ).to.eql( {
+					symbol: 'A$',
+					integer: '9,800,900',
+					fraction: '.32',
+					sign: ''
+				} );
+			} );
+			it( 'CAD', () => {
+				const money = getCurrencyObject( 9800900.32, 'CAD' );
+				expect( money ).to.eql( {
+					symbol: 'C$',
+					integer: '9,800,900',
+					fraction: '.32',
+					sign: ''
+				} );			} );
+			it( 'EUR', () => {
+				const money = getCurrencyObject( 9800900.32, 'EUR' );
+				expect( money ).to.eql( {
+					symbol: '€',
+					integer: '9.800.900',
+					fraction: ',32',
+					sign: ''
+				} );
+			} );
+			it( 'GBP', () => {
+				const money = getCurrencyObject( 9800900.32, 'GBP' );
+				expect( money ).to.eql( {
+					symbol: '£',
+					integer: '9,800,900',
+					fraction: '.32',
+					sign: ''
+				} );
+			} );
+			it( 'JPY', () => {
+				const money = getCurrencyObject( 9800900.32, 'JPY' );
+				expect( money ).to.eql( {
+					symbol: '¥',
+					integer: '9,800,900',
+					fraction: '',
+					sign: ''
+				} );
+			} );
+		} );
+	} );
+} );