Why are we keeping a collection copy?

Tell us what’s happening:

I’m just curious as to what this line is for and exactly why are we using it? There isn’t much explanation about it. Thanks

var collectionCopy = JSON.parse(JSON.stringify(collection));

Your code so far

// Setup
var collection = {
    "2548": {
      "album": "Slippery When Wet",
      "artist": "Bon Jovi",
      "tracks": [ 
        "Let It Rock", 
        "You Give Love a Bad Name" 
    "2468": {
      "album": "1999",
      "artist": "Prince",
      "tracks": [ 
        "Little Red Corvette" 
    "1245": {
      "artist": "Robert Palmer",
      "tracks": [ ]
    "5439": {
      "album": "ABBA Gold"
// Keep a copy of the collection for tests
var collectionCopy = JSON.parse(JSON.stringify(collection));

// Only change code below this line
function updateRecords(id, prop, value) {
  return collection;

// Alter values below to test your code
updateRecords(5439, "artist", "ABBA");

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0.

Link to the challenge:

it changes the object to json then back to javascript, but its already javascript so it doesnt really do anything so I really dont know either

1 Like

It’s been removed in the current version, though that isn’t live yet – it was used to make sure the tests ran properly, but looks to no longer be necessary.

1 Like