gistfile1.js

// res is an empty object that holds an array designers: []
// For each designer object in the inventory...
//   Add an object to the array in res with name: designer.name
//   For each shoe in designer[shoes]...
//     Add shoe price to an array of shoe prices
//   Get the average of the shoe prices
//   Add averagePrice: averageOfShoePrices to the designer's object in res
// return res
function getAverageDesignerPrices(inventory) {
  var res = {'designers':[]};
  for (var designer of inventory) {
    var shoePrices = [];
    for (var shoe of designer['shoes']) {
      shoePrices.push(shoe['price']);
    }
    res['designers'].push({'name':designer.name, 'averagePrice':average(shoePrices)});
  }
  return res;
}

// Find the average of an array of numbers
function average(array) {
  var total = 0;
  for (var num of array) {
    total += num;
  }
  return total / array.length;
}

var expected = {
  'designers': [
    {
      'name': 'Brunello Cucinelli',
      'averagePrice': 1025
    },
    {
      'name': 'Gucci',
      'averagePrice': 850
    }
  ]
};

var inventory = [
  {
    name: 'Brunello Cucinelli',
    shoes: [
      {name: 'tasselled black low-top lace-up', price: 1000},
      {name: 'tasselled green low-top lace-up', price: 1100},
      {name: 'plain beige suede moccasin', price: 950},
      {name: 'plain olive suede moccasin', price: 1050}
    ]
  },
  {
    name: 'Gucci',
    shoes: [
      {name: 'red leather laced sneakers', price: 800},
      {name: 'black leather laced sneakers', price: 900}
    ]
  }
];

function assertObjectsEqual(actual, expected, testName) {
  var passed = true;
  if (Object.keys(actual).length !== Object.keys(expected).length) {
    passed = false;
  } else {
    for (var key in actual) {
      if (actual[key] !== expected[key]) {
        passed = false;
        break;
      }
    }
  }
  if (passed) {
    console.log('passed');
  } else {
    console.log('FAILED [' + testName + '], expected ' + JSON.stringify(expected) + ', but got ' + JSON.stringify(actual));
  }
}

// Test getAverageDesignerPrice via assertObjectsEqual with provided simple paramaters
assertObjectsEqual(getAverageDesignerPrices(inventory), expected, 'Test with provided input and output')