代码在不同环境下表现不同

Question

I've been studying for an upcoming exam and came across something odd. Here is the prompt for the question:

You have a fashion catalog, an inventory of items from various high-fashion designers. Each designer has a lineup of shoes. Each shoe has a name and a price.

It looks like this:

 var currentInventory = [
  {
    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}
    ]
  }
]; 

Your function should return the average cost of all shoes per designer in this format:

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

I've written some code and it behaves differently whether I run it on Repl.it or the hack reactor practice exam website. Here is my code:

function calculateAveragePricePerDesigner(inventory) {
  var result = {designers: []};
  var parsedDesignerAverageCost = [];
  for (i = 0; i < inventory.length; i++) {
    parsedDesignerAverageCost.push(parseAverageCostPerDesigner(inventory[i]));
    console.log(parsedDesignerAverageCost);
  }
  result.designers = parsedDesignerAverageCost;
  return result;
}


function parseAverageCostPerDesigner(currentDesigner) {
  var currentShoes = currentDesigner.shoes;
  var result = {
    name: currentDesigner.name,
    averagePrice: 0
  };
  var cummulativeCost = 0;
  var numOfShoes = currentShoes.length;
  for (i = 0; i < numOfShoes; i++) {
    cummulativeCost += currentDesigner.shoes[i].price;

  }
  var average = cummulativeCost / numOfShoes;
  result.averagePrice = average;
  return result;
}

Is anyone able to explain whether or not my code is correct and possibly why the inconsistency is occurring? On Repl.it my code will compile but not run in a manner that I cannot explain, and on the hack reactor website it will not compile. T Thank you

Answer 1

You have a slight "mistake" here:

 for (i = 0; i < numOfShoes; i++) {

You never declare i . That turns i into an implicit global variable, thus both functions work with the same i . That means that the inner function will increase i, and then the outer will continue with that. Thus it skips some records. The easy fix would be:

 for (var i = 0; i < numOfShoes; i++) {

And this probably has to do with the sample data used to test your code.

---

Here's how I'd write the whole thing:

 function averagePrice(shoes) {
   let sum = 0;
   for(const shoe of shoes)
      sum += shoe.price;
   return sum / shoes.length;
 }

 function task(designers) {
   let result = [];
   for(const designer of designers) {
     result.push({ name: designer.name, averagePrice: averagePrice(designer.shoes) });
    }
    return result;
 }