Record Collection - I don't quite understand it

JavaScript
1

Hello all. I spent several hours trying to figure out this challenge before looking at the solution, but I’m afraid I still don’t understand it. I went through the explanation and tried to comment out the code so it makes sense to me, but I’m still puzzled by 2 sections (which I’ve marked with ? marks.)

In short, what is the purpose and what is the difference between:
collection[id][prop]=[value];
collection[id][prop] = value;

The entire code for reference:

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

function updateRecords(id, prop, value) {
  if (prop === "tracks" && value !== "") //Checks that Prop is "Tracks" and Value is not a blank string.
  {
    if(collection[id][prop]) {
      collection[id][prop].push(value); //Adds Value to the Tracks array.
    } else {
    collection[id][prop]=[value]; //Value is updated? to the Tracks array.
    }
   } else if (value !== "") { //Checks if Value is not a blank string.
    collection[id][prop] = value; //Value is updated? to the Tracks array.
  } else {
    delete collection[id][prop]; //Value is a blank string. Ergo removes the Prop from the object.
  }
   // console.log (collection[id][prop]);
  return collection;
}

// Alter values below to test your code
console.log (collection);
updateRecords(5439, "artist", "ABBA");
console.log (collection);
2

Using bracket and dot notations you can access values nested in an object.
For example,

collection[“2548”][“album”] will return “Slippery When Wet”.
By passing in different values for variables id and prop, you are accessing their corresponding values.

Then they are using = operators to assign values to them or replacing already existing values.

[value]
value

Difference between these two on the right side of equal operators are simply one is in an array and the other isn’t.

1 Like
3

OH! Okay! The Tracks section of the collection is an array. And we know it’s pointing at the Tracks because of the first If statement. And we know the If/Else statement is pointing at Album or Artist. This lesson is complicated but I think I understand it better now.

So in this case my comments should be:
collection[id][prop]=[value]; //Value is updated to the Tracks array.
and
collection[id][prop] = value; //Value is updated to Album or Artist property.