total-price.js

var items = [{'price': 123, 'tax': 0.1}, {'price': 234, 'tax': 0.3}];

var taxCalculator = function (items) {
        
    var taxedMapper = function (item) {
        return item.price + item.price * item.tax;
    };
    
    var nonTaxedMapper = function (item) {
        return item.price;
    };
    
    var total = function (items, mapper) {
        var total = items.map(mapper).reduce(function (totalPrice, currentPrice) {
            return totalPrice + currentPrice;
        }, 0);
        return total;
    }


    return {
        taxedTotal: total.bind(null, items, taxedMapper),
        nonTaxedTotal: total.bind(null, items, nonTaxedMapper)
    }
};

var calc = taxCalculator(items);
calc.taxedTotal();
calc.nonTaxedTotal();

total-price.py

items = [{"price": 123, "tax": 0.1}, {"price": 234, "tax": 0.3}]

class TaxCalculator(object):
  def __init__(self, items):
    self.items = items
  
  def taxedTotal(self):
    return sum([item["price"]+ item["price"] * item["tax"] for item in self.items])
  
  def nonTaxedTotal(self):
    return sum(item["price"] for item in self.items)

calc = TaxCalculator(items)

calc.taxedTotal()
calc.nonTaxedTotal()