@restorecommerce/cart

An backend agnostic purely data-driven shopping cart that can be used on client- and server side.

Features

• Item handling (add, remove etc.)
• VAT calculation with extensible tax model
  • EU tax calculation built-in (for sub-threshold based taxation)
• Shipping cost calculation based on selected courier and plan
• Extensibility for adding couriers
• Totals calculation based on items, taxes and shipping
• Can run completely offline
• Local storage on browsers via pluggable serializers
• Back-end agnostic
• Fully typed

Usage

Basic Example

Cart Instantiation:

const cart = new Cart({
  serializer: new MockSerializer(),
  shippingMethod: new Courier({
    source: JSON.stringify(data.publicDHL),
    shipping: {originCountry: 'DE'}
  }),
  taxOriginCountry: 'DE',
  taxes: {
    vat_standard: {
      rate: new Decimal(1.19),
      desc: '+ VAT 19%'
    },
    vat_reduced: {
      rate: new Decimal(1.07),
      desc: '+ VAT 7%'
    }
  }
});

Setting serializer and shippingMethod is optional.

setDestinationCountry(country: string)

cart.setDestinationCountry('LV');

getShippingMethod()

cart.getShippingMethod();

Output:

Courier {
  _source: {
    assumptions: {
      currency: 'eur',
      dimensions: [Object],
      length: 'mm',
      ranges: [Object],
      weight: 'gram'
    },
    zones: {
      '1': [Object],
      '2': [Object],
      '3': [Object],
      '4': [Object],
      '5': [Object],
      '6': [Object],
      '7': [Object],
      '8': [Object],
      national: [Object]
    }
  },
  _shipping: {
    destinationCountry: 'LV',
    originCountry: 'DE' }
}

getShipping()

There is no setShipping setter, since info about shipping is taken from ShippingMethod's source property.

cart.getShipping(); // calculates shipping cost

Output:

{
  price: '15.99',
  taxType: 'vat_standard',
  maxWeight: 5000,
  type: 'package',
  zone: '1',
  human: {
    zone: '1 (all EU countries)',
    offer: 'Package up to 5kg',
  }
}

getSerializer()

cart.getSerializer();

getTaxRates()

cart.getTaxRates();

Output:

{
  taxes: {
    vat_standard: {
      rate: '1.19',
      desc: '+ VAT 19%'
    },
    vat_reduced: {
      rate: '1.07',
      desc: '+ VAT 7%'
    }
  }
}

addItems(items: IItem[])

cart.addItems([{
  sku: 'cr2-blue',
  price: new Decimal('12.95'), // Price
  taxType: 'vat_reduced',
  weight: 210, // grams
  height: 2.20, // cm
  width: 13.5, // cm
  depth: 8.22, // cm
  quantity: 7,
}, {
  sku: 'cr5-red',
  price: new Decimal('1.10'),
  taxType: 'vat_standard',
  weight: 210, // grams
  height: 2.20, // cm
  width: 13.5, // cm
  depth: 8.22, // cm
  quantity: 15,
}, {
  sku: 'cr3-yellow',
  price: new Decimal('2.48'),
  taxType: 'vat_standard',
  weight: 210, // grams
  height: 2.20, // cm
  width: 13.5, // cm
  depth: 8.22, // cm
  quantity: 3,
}]);

remItem(sku: string)

cart.remItem('cr3-yellow');

getItems()

cart.getItems();

Output:

[
  {
    sku: 'cr2-blue',
    price: 12.95,
    taxType: 'vat_reduced',
    weight: 210,
    height: 2.2,
    width: 13.5,
    depth: 8.22,
    quantity: 7
  },
  {
    sku: 'cr5-red',
    price: 1.10,
    taxType: 'vat_standard',
    weight: 210,
    height: 2.2,
    width: 13.5,
    depth: 8.22,
    quantity: 15
   }
]

setCustomer(customer: ICustomer)

cart.setCustomer({
  type: CustomerType.COMMERCIAL,
});

setCustomerType(type: CustomerType)

This modifies the customer..

cart.setCustomerType(CustomerType.PRIVATE);

getCustomer()

cart.getCustomer();

Output:

{
  type: 1 // 0 - COMMERCIAL / 1 - PRIVATE
}

modifyItem(item: any)

cart.modifyItem({
  sku: 'cr5-red',
  // no update for other Cart properties as no change
  quantity: 10, // change only quantity
});

modifyItemQuantity(sku: string, quantity: number)

cart.modifyItemQuantity('cr5-red', 5); // adds 5 to initial quantity

getItemQuantity(sku: string)

`Amount of cr2-blue = ${cart.getItemQuantity('cr5-red')}`;

Output:

Amount of cr5-red = 15 // 10 + 5

getItemCount()

`Amount of unique products = ${cart.getItemCount()}`;

Output:

Amount of unique products = 2

getGrandQuantity()

`Amount of all products = ${cart.getGrandQuantity()}`;

Output:

Amount of all products = 22 // 15 + 7

getTaxes(keepOriginalTaxType?: boolean )

cart.getTaxes();

Output:

netPrice and rate are instances of Decimal.

{
  vat_standard: {
    netPrice: '32.49',
    rate: '1.19',
    desc: '+ VAT 19%'
  },
  vat_reduced: {
    netPrice: '90.65',
    rate: '1.07',
    desc: '+ VAT 7%'
  }
}

static round(money: Money)

Parameter could be number|string|Decimal. Returns string.

Cart.round(1.120); // '1.12'
Cart.round('1.123'); // '1.13'
Cart.round(new Decimal(1.125)); // '1.13'
Cart.round(new Decimal('1.127')); // '1.13'

getTotalNet()

Total net (without taxes).

Cart.round(cart.getTotalNet()); // '123.14'

Calculation:

1) customer.billing.countryCode === 'LV' => VAT + 19% / 7%
2) cr2_blue: Price * quantity => 12.95 * 7  = 90.65
3) cr5_red:  Price * quantity => 1.10 * 15  = 16.5
4) Max Weight of all items = 22 items * 210 grams  = 4620 grams =>
shipping = 15.99 euro for package less than 5000 grams to EU
5) sum = 90.65 + 16.5 + 15.99 = 123.14

getTotalGross()

Total gross (with taxes).

Cart.round(cart.getTotalGross()); // '135.66'

Calculation:

1) cr2_blue => cr2_blue + VAT 7% = 90.65 * 1.07 = 96.9955
2) cr5_red => cr5_red + VAT 19% = 16.5 * 1.19 = 19.635
3) shipping => shipping + VAT 19% = 15.99 * 1.19 = 19.0281
4) sum  =>  96.9955 + 19.635 + 19.0281 = 135.6586
5) round(135.6586) = 135.66

Tests

More examples of using the Cart can be found in test/index.ts.

Reference

|Method | Description | |---|---| |getItems(): IItems / undefined | Get Items | |private setItems(items: IItem[]): void| Set items | |getCustomer(): ICustomer / undefined| Get customer | |setCustomer(customer: ICustomer): void| Set customer | |getShippingMethod(): IShippingMethod/ undefined| Get shipping method | |setShippingMethod(shippingMethod: IShippingMethod): void| Set shipping method | |getSerializer(): ISerializer / undefined| Get serializer | |setSerializer(serializer: ISerializer): void| Set serializer | |getTaxRates(): TaxRates| Get tax rates | |private setTaxRates(taxRates: TaxRates)| Set tax rates | |setCustomerType(type: CustomerType): void | Set customer's type (PRIVATE/COMMERCIAL) | |setDestinationCountry(country: string): void| Set destination country | |addItems(items: IItem[]): void | Add item/items to the cart | |remItem(sku: string): void| Remove item from the cart by SKU (Stock Keeping Unit) | |modifyItem(item: any)| Update item | |modifyItemQuantity(sku: string, quantity: number): void | Modify item's quantity | |getItemCount(): number | Get item count | |getItemQuantity(sku: string): number | Get quantity of particular item | |getGrandQuantity(): number | Item count x quantity of each item | |getTaxes(keepOriginalTaxType?: boolean ): { [taxType: string]: { netPrice: Decimal, rate: Decimal, desc: string, price: Decimal } } | Get tax list, with ratios and additive costs | |getTotalNet(): number | Get sum of item and shipping costs (taxes excluded) | |getTotalGross(): number| Get sum of item and shipping costs (taxes included) | |getShipping(): { price: Money, [prop: string]: any } | Get item's shipping info | |static round(money: Money): string | Convert money type (number/string/Decimal) to string with rounding |

Development

To lint, transpile and test, run:

npm test

Couriers

IShippingMethod interface implementations:

• Courier
• SelfPickUp

Courier Plans:

• DHL premium business based on contract based pricing not publicly available.
• DHL private customers based on private customer pricing info pdf | de | intl | web
• DHL express based on contract based pricing not publicly available.

Calculation Logic

Taxes

For VAT calculation, the cart applies the EU ruleset for taxation which is exemplified in the following with a shop that is located in Germany and customer location location/ type being:

• Germany private: VAT applies
• Germany commercial: VAT applies
• Other EU countries private: VAT applies
• Other EU countries commercial: VAT free
• Non-EU countries private: VAT free
• Non-EU countries commercial: VAT free

This also works for other countries as it's just a simplification of this for most countries. Sales taxes and other country specific taxes can be added.

Legal background:

• EU shipments, private
• EU shipments, commercial
• Non-EU shipments