advanced-reduce

reducers.js

let selected = [
  { price: 20   },
  { price: 45   },
  { price: 67   },
  { price: 1305 }
];

let reducers = {
  rubles : (state, item) => { return state.rubles  += item.price            },
  dollars: (state, item) => { return state.dollars += item.price / 71.6024  },
  euros  : (state, item) => { return state.euros   += item.price / 79.0133  },
  yens   : (state, item) => { return state.yens    += item.price / 0.6341   },
  pounds : (state, item) => { return state.pounds  += item.price / 101.7829 }
};

let combineReducers = reducers => {
  return (state, item) => {
    return Object.keys(reducers).reduce( (nextState, key) => {
      reducers[key](state, item);
      return state;
    }, {});
  }
};

let priceReducer = combineReducers(reducers);
let totalPrice = selected.reduce(priceReducer, {
  rubles: 0, 
  pounds: 0, 
  dollars: 0,
  euros: 0,
  yens: 0
});

console.log(totalPrice);