Record Collection Confusion

JavaScript
1

Tell us what’s happening:

Hello I just want to know what’s happening with this code


 else if (prop === "tracks") {
  collection[id][prop] =  collection[id][prop] || [];

what does it do? to be exactly straightforward what does collection[id][prop] = collection[id][prop] || []; do?

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"
}
};

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

if (value === "") {
  delete  collection[id][prop];
} else if (prop !== "tracks" && value !== "") {
  collection[id][prop] = value;
} else if (prop === "tracks") {
  collection[id][prop] =  collection[id][prop] || [];
}



return collection;
}

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

console.log(updateRecords(1245, "tracks", "Addicted to Love"));

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 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

If collection[id][prop] already has a truthy value (for example if it already has an array), it effectively does nothing. Otherwise it assigns an empty array to collection[id][prop]

1 Like
3

But truthy You mean something like if tracks = [] ? Sorry I’m really confused is there any way to visualize this?

4

false, 0, 0n, "" (empty string), undefined, null and NaN are falsey values, ie they coerce to false.

All other values are truthy, ie they coerce to true.

This is important to understand JavaScript: it is covered earlier in the course, but as a refresher:

1 Like
5

thank you! :slight_smile:

1 Like