vehicle-purchase.js

// @ts-check
//
// The line above enables type checking for this file. Various IDEs interpret
// the @ts-check directive. It will give you helpful autocompletion when
// implementing this exercise.

/**
 * Determines whether or not you need a licence to operate a certain kind of vehicle.
 *
 * @param {string} kind
 * @returns {boolean} whether a license is required
 */
export function needsLicense(kind) {
  return ['car', 'truck'].includes(kind)
}

/**
 * Helps choosing between two options by recommending the one that
 * comes first in dictionary order.
 *
 * @param {string} option1
 * @param {string} option2
 * @returns {string} a sentence of advice which option to choose
 */
export function chooseVehicle(option1, option2) {
  const alphabeticalFirst = [option1, option2].sort().shift()
  return `${alphabeticalFirst} is clearly the better choice.`
}

/**
 * Calculates an estimate for the price of a used vehicle in the dealership
 * based on the original price and the age of the vehicle.
 *
 * @param {number} originalPrice
 * @param {number} age
 * @returns {number} expected resell price in the dealership
 */
export function calculateResellPrice(originalPrice, age) {
  if (age < 3) { return originalPrice * 0.8 }
  if (age <= 10) { return originalPrice * 0.7 }
  return originalPrice * 0.5
}