Google Apps Script function to denormalize json data working erratically - google-apps-script

Question

I have a function to denormalize json data.
Json data looks like:
-entries
- entry
- skus
What I am trying to do is to create an array of objects where entries with more than 1 SKUs should be repeated the x times, where x is the number of skus (length of the sku array); each time switching the data of the skus.
The problem is that the sku data does not switch, and the same skus are shown multiple times in the resulting array.
When I debug step by step, the array is appended fine at the beginning, however when function proceeds the correctly appended elements of the array are overwritten.
Here the function code:
let data = [
{
name: 'a',
skus: [1, 2],
},
{
name: 'b',
skus: [3, 4],
},
{ name: 'c', skus: [5] },
{ name: 'd', skus: [6, 7, 8] },
];
function flatten(data) {
let newArray = [];
for (i in data) {
const el = {};
el.name = data[i].name;
let skus = data[i].skus;
for (j in skus) {
el.sku = skus[j];
newArray.push(el);
console.log(el);
}
}
return newArray;
}
what I am trying to achieve is to return a new array which is so:
[
{ name: a,
sku: 1
},
{ name: a,
sku: 2
},
{
name: b,
sku: 3,
},
{
name: b,
sku: 4,
}... and so on ]
Thanks

Answer 1

You want to achieve the following conversion.
From
const data = [
{name: 'a', skus: [1, 2]},
{name: 'b', skus: [3, 4]},
{name: 'c', skus: [5]},
{name: 'd', skus: [6, 7, 8]},
];
To
[
{"name": "a", "sku": 1},
{"name": "a", "sku": 2},
{"name": "b", "sku": 3},
{"name": "b", "sku": 4},
,
,
,
]
Modification points:
I think that the reason of your issue is due to the call by reference. When the object el is put to the array with newArray.push(el), el is changed by the next loop. By this, I think that your issue occurs. In this case, it is required to copy the object and put to the array.
When above points are reflected to your script, it becomes as follows.
Modified script:
From:
newArray.push(el);
To:
newArray.push(Object.assign({}, el));
Testing:
let data = [
{name: 'a', skus: [1, 2]},
{name: 'b', skus: [3, 4]},
{name: 'c', skus: [5]},
{name: 'd', skus: [6, 7, 8]},
];
function flatten(data) {
let newArray = [];
for (i in data) {
const el = {};
el.name = data[i].name;
let skus = data[i].skus;
for (j in skus) {
el.sku = skus[j];
newArray.push(Object.assign({}, el));
// console.log(el);
}
}
return newArray;
}
console.log(flatten(data))
Other pattern:
In your case, the following script can be also used.
const data = [
{name: 'a', skus: [1, 2]},
{name: 'b', skus: [3, 4]},
{name: 'c', skus: [5]},
{name: 'd', skus: [6, 7, 8]},
];
const res = data.reduce((ar, {name, skus}) => {
skus.forEach(e => ar.push({name: name, sku: e}));
return ar;
}, []);
console.log(res);
Reference:
Object.assign()