From Twitter discussion: https://twitter.com/karlhorky/status/736512469800235012

promise.js

function getOrderDetails(orderID) {
	return db.find( "orders", orderID ).then(order =>
		db.find( "customers", order.customerID ).then(customer => ({order, customer}))
	).then(({order, customer}) =>
		Object.assign(order, {customer})
    	);
}

getOrderDetails( 1234 )
.then( displayOrder, showError );