Basic JavaScript - Record Collection

Hi all, could someone explain why dot notation isn’t working here, please?

EDIT: Found the error in the code where “value” wasn’t sqare bracketed to create initially absent array.
Still not sure why dot notation won’t work.


// Setup
const recordCollection = {
  2548: {
    albumTitle: 'Slippery When Wet',
    artist: 'Bon Jovi',
    tracks: ['Let It Rock', 'You Give Love a Bad Name']
  2468: {
    albumTitle: '1999',
    artist: 'Prince',
    tracks: ['1999', 'Little Red Corvette']
  1245: {
    artist: 'Robert Palmer',
    tracks: []
  5439: {
    albumTitle: 'ABBA Gold'

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

if (prop !== "tracks" && value !== "") { = value;

} else if (prop === "tracks" &&"tracks") === false) { = [value];

} else if (prop === "tracks" && value !== "") {;

} else if (value === "") {



  return records;

updateRecords(recordCollection, 5439, 'artist', 'ABBA');

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Challenge: Basic JavaScript - Record Collection

Link to the challenge:

When using dot notation to access a property, the property name or identifier must not start a with a number. All the record collection keys are numbers, so that’s why the dot notation is not working.
(to test this, change all the numbers to letters like a b c d and then try to use the dot notation then and it will work)

1 Like

Thanks, this makes sense.
However it doesn’t seem to work if I bracket ids only, like this:
records[id].prop = [value]

I don’t think you can mix notations like this. (you should pick one method)
But also I just realized that dot notation doesn’t work with variables. It works with identifiers (so the name of the property but not the variable that contains the name of the property)

1 Like

Yes, you’re right. I totally forgot about that part, thinking about spaces in the names.
It’s a bummer about notation mixing, though.

to be honest, I’m not 100% sure about that. You can try and see if you can get it to work…
Edit: i just tried it and it worked. So i guess it is allowed after all…

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