composePractise_9.js

// Setup
//==============
const _ = R;
const { formatMoney } = accounting;

// Example Data
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: "Audi R8", horsepower: 525, dollar_value: 114200, in_stock: false },
    { name: "Aston Martin One-77", horsepower: 750, dollar_value: 1850000, in_stock: true },
    { name: "Pagani Huayra", horsepower: 700, dollar_value: 1300000, in_stock: false }
];

// Exercise 1:
// ============
// use _.compose() to rewrite the function below. Hint: _.prop() is curried.
// const x = h(g(f(cars))) = compose(h, g, f)

const isLastInStock = _.compose(_.prop('in_stock'), _.last)


QUnit.test("Ex1: isLastInStock", assert => {
    assert.deepEqual(isLastInStock(CARS), false);
})


// i solved in code pen, if u need to run, go to this website
// https://codepen.io/Tidalu/pen/YzRqPKb?editors=0010 cuz there is not 



// Exercise 2:
// ============
// use _.compose(), _.prop() and _.head() to retrieve the name of the first car

const nameOfFirstCar = _.compose(_.prop('name'), _.head);

QUnit.test("Ex2: nameOfFirstCar", assert => {
    assert.equal(nameOfFirstCar(CARS), "Ferrari FF");
})

// Exercise 3:
// ============
// Use the helper function _average to refactor averageDollarValue as a composition

const _average = function (xs) { return _.reduce(_.add, 0, xs) / xs.length; }; // <- leave be

const averageDollarValue_ = _.compose(_average, _.map, _.prop('dollar_value'))


//       function(cars) {
//   const dollar_values = _.map(_.prop('dollar_value'), cars);
//   return _average(dollar_values);
// };
var func = c => c.dollar_value;
var averageDollarValue = _.compose(_average, _.map(_.prop('dollar_value')));

//     function(cars) {
//   var dollar_values = _.map(function(c) { return c.dollar_value; }, cars);
//   return _average(dollar_values);
// };

QUnit.test("Ex3: averageDollarValue", assert => {
    assert.equal(averageDollarValue(CARS), 790700);
})


// Exercise 4:
// ============
// Write a function: sanitizeNames() using compose that returns a list of lowercase and underscored names: e.g: sanitizeNames(["Hello World"]) //=> ["hello_world"].

// const _underscore = _.curry((x) => x.replace(/\W+/g, '_'));//
const _underscore = _.replace(/\W+/g, '_');//  <-- leave this alone and use to sanitize
const map = _.curry((f, x) => x.map(f));
// const sanitizeNames_ = _.compose( _.map( _.toLower), _.map( _underscore), _.map( _.prop('name')))
const sanitizeNames = map(_.compose(_.toLower, _underscore, _.prop('names')))

// QUnit.test("Ex4: sanitizeNames", assert => {
//   assert.deepEqual(sanitizeNames(CARS), ['ferrari_ff', 'spyker_c12_zagato', 'jaguar_xkr_s', 'audi_r8', 'aston_martin_one_77', 'pagani_huayra']);
// })



// Bonus 1:
// ============
// Refactor availablePrices with compose.

// const availablePrices = function(cars) {
//   const available_cars = _.filter(_.prop('in_stock'), cars);
//   return available_cars.map(x => formatMoney(x.dollar_value)).join(', ');
// }
const availablePrices = _.compose(
    _.join(', '),
    _.map(_.compose(formatMoney, _.prop('dollar_value'))),
    _.filter(_.prop('in_stock'))
)

QUnit.test("Bonus 1: availablePrices", assert => {
    assert.deepEqual(availablePrices(CARS), '$700,000.00, $1,850,000.00');
})

// Bonus 2:
// ============
// Refactor to pointfree.
const _concat = (a, x) => a + x;
// const fastestCar = function(cars) {
//   const sorted = _.sortBy(car => car.horsepower, cars);
//   const fastest = _.last(sorted);
//   return fastest.name + ' is the fastest';
// }
const _append = _.flip(_.concat)
const fastestCar = _.compose(
    _append(' is the fastest'),
    _.prop('name'),
    _.last,
    _.sortBy(_.prop('horsepower'))
);

QUnit.test("Bonus 2: fastestCar", assert => {
    assert.equal(fastestCar(CARS), 'Aston Martin One-77 is the fastest');
})