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) {
    cars.push({type: type, price: price, year: year})
}

  this.getSumPrice = function() {
    var result = 0;
    cars.forEach(function(car) {
      result += car.price
    });
      return result;
  };

  this.getOldestCarType = function() {
    var oldest = cars[0];
      for (var i = 0; i < cars.length; i++) {
        if (oldest.year > cars[i].year) {
          oldest = cars[i];
        }
      }
      return oldest.type;
  };

  this.deleteCarByType = function(car) {
    for (var i = 0; i < cars.length; i++) {
      if (cars[i].type === car) {
        cars.splice(i, 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