5.js

'use strict';

// Create a constructor called CarStore, that takes an array of cars as a parameter:
// It should have an "addCar" method that adds a car object to it's list
// It should have a "getSumPrice" method that returns the sum of all cars price
// It should have a "getOldestCarType" method that returns the oldest car's type
// It should have a "deleteCarByType" method that removes the cars from the inner list
// that have the given type

function CarStore(cars) {
  this.cars = cars || [];
  this.addCar = function (type, price, year) {
    this.cars.push({type: type, price: price, year: year});
  }

  this.getSumPrice = function () {
    return this.cars.reduce(function (sum, next) {
      return sum += next.price;
    }, 0);
  }

  this.getOldestCarType = function () {
    var oldest = this.cars[0];
    this.cars.forEach(function (car) {
      if (car.year < oldest.year) oldest = car;
    });
    return oldest.type;
  }

  this.deleteCarByType = function (type) {
    var cars = this.cars;
    cars.forEach(function (car) {
      if (car.type === type) {
        var index = cars.indexOf(car);
        cars.splice(index, 1);
      }
    });
  }
}

var cars = [
  {type: 'Dodge', price: 20000, year: 2012},
  {type: 'Tesla', price: 30000, year: 2015},
  {type: 'Nissan', price: 12000, year: 2010},
  {type: 'Trabant', price: 2000, year: 1980},
  {type: 'Ferrari', price: 40000, year: 2001}
];

var carStore = new CarStore(cars);

carStore.addCar('Smart', 18000, 2011);
console.log(carStore.getSumPrice()); // 122000
console.log(carStore.getOldestCarType()); // 'Trabant'
carStore.deleteCarByType('Ferrari');
console.log(carStore.getSumPrice()); // 82000