Record Collection: push rewrites array with pushed element

JavaScript
1

Tell us what’s happening:
This challenge has cost me several hours of my life and I could really use some help with it.
I came up with a working solution, though I thought I could make it better, and this is where things got frustrating.
I use collection[id].tracks.push(value) in the working solution and things look bright, but in the code below it doesn’t append an element to the “tracks” array, but replaces all its elements.

What am I doing wrong?

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: [
     "1999",
     "Little Red Corvette"
   ]
 },
 1245: {
   artist: "Robert Palmer",
   tracks: [ ]
 },
 5439: {
   album: "ABBA Gold"
 }
};

function updateRecords(id, prop, value) {
  console.log(id, prop, value);
  if (value ===""){ // value empty
    delete collection[id][prop];
  } else { 
    if (prop !== "tracks"){ // value not empty, prop is not "tracks"
      collection[id][prop]=value;
    } else { // value not empty and prop is "tracks" !!! ERROR HAPPENS HERE - collection[id].tracks.push(value) resets "tracks" only to the `value` and drops other elements;
      if (collection.hasOwnProperty("tracks")) {
        collection[id].tracks.push(value);
      } else { // value not empty, prop is "tracks" and album has no "tracks"
        collection[id].tracks = [];
        collection[id].tracks.push(value);
      }
    }
  } 
 
 console.log(collection[id]);
 return collection;
 
}

// Alter values below to test your code
updateRecords(5439, "artist", "ABBA");
updateRecords(2468, "tracks", "sample track");
updateRecords(2548, "tracks", "sample track");

my logs are:
{“album”:“ABBA Gold”,“artist”:“ABBA”}
{“album”:“1999”,“artist”:“Prince”,“tracks”:[“sample track”]}
{“album”:“Slippery When Wet”,“artist”:“Bon Jovi”,“tracks”:[“sample track”]}

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36.

Challenge: Record Collection

Link to the challenge:
https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-javascript/record-collection

2

it is little things that trip us… look carefully at the code I quoted. Do you see it?

1 Like
3

Wow, thank you! It took me about 5 munutes to see it :slight_smile: You must have an eye of an eagle!

4

it is just a common error for this challenge, after having seen it many times…

with practice you will also become better at spotting these things!

one thing one could do to avoid these errors is to create a variable at the beginning like let record = collection[id] and then you reference always variable record, instead of having to remember to access the right object with the id
You can do this because doing let record = collection[id] you are just changing the reference of the object, not copying it. Arrays do the same. If you want to copy an array or object you need something a tad more complex.

1 Like
5

Thank you, it’s so cool! I did not know one could do that.