const fp = require('lodash/fp')
// 数据
// horsepower马力，dollar_value价格，in_stock库存
const cars = [
  {name: 'Ferrari FF', horsepower:660, dollar_value:700000, in_stock:true},
  {name: 'Spyker C12 Zagato', horsepower:650, dollar_value:648000, in_stock:false},
  {name: 'Jaguar XKR-S', horsepower:550, dollar_value:132000, in_stock:false},
  {name: 'Ferrari', horsepower:525, dollar_value:114200, in_stock:false},
  {name: 'Aston Martin One-77', horsepower:750, dollar_value:1850000, in_stock:true}
]

let _average = function (xs) {
  return fp.reduce(fp.add, 0 , xs)/xs.length
}

// let averageDollarValue = function (cars) {
//   let dollar_value = fp.map(function (car) {
//     return car.dollar_value
//   },cars)
//   return _average(dollar_value)
// }

let dollar_value = function (cars) {
  return fp.map(fp.prop('dollar_value'), cars)
}

const f = fp.flowRight(_average, dollar_value)

console.log(f(cars));