Basic JavaScript - Record Collection Clarification Needed

JavaScript
1

I just have a question regarding how I did things.

function updateRecords(records, id, prop, value) {
if (value == “” ){
delete records[id][prop];
}
return records;
}

This code worked for me but previously I had tried:

delete records.id.prop;

Could someone clarify to me why the second one(above) did not work?

many thanks!

Challenge: Basic JavaScript - Record Collection

Link to the challenge:

2

Dot notation cannot work with a variable holding the name of the property. If you are using a variable to say what property you are accessing, bracket notation is mandatory.

3

This is a useful explainer I think:

4

When you say “variable holding the name of a property” you mean in this case either ID or PROP?
And sorry but just to clarify, why is this example ok then?

const ourStorage = {
  "desk": {
    "drawer": "stapler"
  },
  "cabinet": {
    "top drawer": { 
      "folder1": "a file",
      "folder2": "secrets"
    },
    "bottom drawer": "soda"
  }
};

ourStorage.cabinet["top drawer"].folder2;
ourStorage.desk.drawer;

See at the end the tutorial was accessing ourStorage.desk.drawer; which would come out to be “stapler”, why is this considered different ?

5

This helped alot thank you. So I can only recall keys assigned through variables via bracket recall.

So am I correct in saying when :
function updateRecords(records, id, prop, value)
occured it created the variables id, prop, value and because this was created then the only way to recall was via bracket notation?

6

Yes, if you are using function parameters (or any other variables) rather than explicit object properties, then you must use bracket notation.

7

Thanks, and just one last question , is this an easy mistake to make for a beginner or was this distinction meant to be easy enough for me to spot the first time by myself? I felt stupid I couldn’t figure it out at first.

8

No, there’s so much stuff to learn that we can’t possibly be expected to understand or remember everything. I think the dot/bracket distinction is explained somewhere in the objects part of the Javascript curriculum, but I can’t remember where to be honest.

You should always feel completely free to ask questions about anything which you don’t understand - that’s what this community is here for!

2 Likes
9

Both id and prop are variables. That means they can be used as properties in dot notation

10

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