const sum = (...args) => {

const sum = args.reduce((acc, item) => {

return acc + item;

}, 0)

return sum;

}

const vowelize = (arr) => {

const regex = /[AEIOUaeiou]/

const vowelArr = arr.map(word => {

return word.split('').filter(letter => letter.match(regex)).join('');

})

const result = vowelArr.filter(word => word !== '');

return result;

}

const combineAndSort = (...args) => {

const flatArr = [...args].flat().sort();

return flatArr;

}

const anagramTester = (a, b) => {

const wordA = a.toLowerCase().split(' ').join('');

const wordB = b.toLowerCase().split(' ').join('');

const objA = {};

const objB = {};

for(const letter of wordA) {

objA[letter] ? objA[letter] += 1 : objA[letter] = 1;

}

for(const letter of wordB) {

objB[letter] ? objB[letter] += 1 : objB[letter] = 1;

}

const keysA = Object.keys(objA)

const keysB = Object.keys(objB)

if(keysA.length !== keysB.length) return false;

for(let key of keysA){

if(objA[key] !== objB[key]) return false;

}

return true;

}

const objectForEach = (obj, callback) => {

for(const key in obj){

callback(obj[key]);

}

}

const updateAtPath = (obj, string, value) => {

const keyArr = string.split('.');

const firstKeys = keyArr.slice(0, keyArr.length - 1);

const lastKey = keyArr.slice(keyArr.length - 1);

const resultPath = firstKeys.reduce((acc, key) => {

return acc[key];

}, obj)

resultPath[lastKey] = value;

}

class Car {

constructor({initialFuelLevel, fuelCapacity}) {

this.fuelLevel = initialFuelLevel;

this.fuelCap = fuelCapacity;

}

getFuelLevel = () => {

return this.fuelLevel;

}

addFuel = (fuel) => {

this.fuelLevel += fuel;

if(this.fuelLevel > this.fuelCap) this.fuelLevel = this.fuelCap;

}

}

const whatWouldYouLikeToCheckOut = async (libraryApi) => {

const books = [];

const authors = await libraryApi['favoriteAuthors']();

const results = await Promise.all(authors.map(author => libraryApi['booksAvailableBy'](author)));

results.flat().forEach(book => {

if(book.author) books.push(book.title);

})

return books;

}

const calc = (left) => {

return (operator) => {

return (right) => {

return eval(`${left}${operator}${right}`);

}

}

}

module.exports = {

exampleFunction: function(message) { return message; },

sum,

vowelize,

combineAndSort,

anagramTester,

objectForEach,

updateAtPath,

Car,

whatWouldYouLikeToCheckOut,

calc

}