var bill = new Bill(); //new Bill
bill.charges.new({ price: 1.2 }); //add charge

var charge = bill.charges.new({ qty: 2.5, price: 2.4}); //charge with quantity
charge.modify({ fixedValue: 1.5 }); //charge modifier

bill.charges.new({ price: 3, modifier: { percentRatio: 0.5 } }); //charge with percent modifier
bill.modifiers.new({ percentRatio: -0.1 }); //global modifier percent
bill.payments.new({ value: 1 }); //partial payment
bill.payments.new(); //pay the rest

var Bill = billing.BillingBill;
var Charge = billing.BillingCharge;
var Modifier = billing.BillingModifier;
var Payment = billing.BillingPayment;

var bill = new Bill();
new Charge({ bill: bill, price: 1.2 });

var charge = new Charge({ bill: bill, qty: 2.5, price: 2.4});
new Modifier({ charge: charge, fixedValue: 1.5 });

new Charge({ bill: bill, price: 3, modifier: { percentRatio: 0.5 } })

new Modifier({ bill: bill, percentRatio: -0.1 });

$3

= .new(attributes = {}) //create
boolean .add(item) //add
boolean .remove(item) //destroy

$3

boolean .isValid // check validity
.errors // errors format [{ propertyName: { validationName: 'Human readable error' }}]

$3

.state // Unused instance variable available for UI purposes

Using the nomenclature (samples/node/usingNomenclature.js)

billing.config({
nomenclature: {
taxGroups: [
{ id: 1, name: '20%', percentRatio: 0.2 },
{ id: 2, name: '9%', percentRatio: 0.09 }
],
departments: [
{ id: 1, name: 'Food', taxGroupId: 1 },
{ id: 2, name: 'Accommodation', taxGroupId: 2 }
],
plus: [
{ id: 1, name: 'Pizza', departmentId: 1, price: 20.5 },
{ id: 2, name: 'Steak', departmentId: 1, price: 30.2 },
{ id: 3, name: 'Room', departmentId: 2, price: 200 }
],
paymentTypes: [
{ id: 1, name: 'Cash', isCash: true, isFiscal: true },
{ id: 2, name: 'Card', isCash: false, isFiscal: true },
{ id: 3, name: 'External', isCash: false, isFiscal: false }
]
}
});

var bill = billing.bills.new();

bill.charges.new({ pluId: 1 }); // -> { qty: 1, price: 20.5, name: 'Pizza', taxRatio: 0.2 }
bill.charges.new({ qty: 2, price: 150, departmentId: 2 });
bill.payments.new({ paymentTypeId: 1 }); // -> { name: 'Cash', value: 20.5, isCash: true, isFiscal: true }