Google form: create two rows with different information - google-apps-script

Question

Im trying to create a google form with 2 fields, one for "item" and the other for "quantity"
Since user might need to send miltiple items I want to create 1 form only and sort the information.
my Google form
So far I have managed to add a script that splits the information submitted in "item" into many rows, however, Im not able to do the same with the field "quantity"
I got this information from this post
This is my script:
function onFormSubmit(e) {
var ss = SpreadsheetApp.openByUrl("URL_here");
var sheet = ss.getSheetByName("FormResponses");
// Form Response retrieved from the event object
const formResponse = e.response;
var itemResponses = formResponse.getItemResponses();
// Add responses comma-separated included
var rowData = itemResponses.map(item => item.getResponse().toString());
rowData.splice(0, 0, formResponse.getTimestamp());
// Split into different rows afterwards
if (rowData[1].includes(',')) {
rowData[1].split(',').forEach(instanceName => {
let tmpRow = rowData.map(data => data);
tmpRow[1] = instanceName;
sheet.appendRow(tmpRow);
// Append to the sheet
});
}
else {
sheet.appendRow(rowData); // Append to the sheet
}
Current results:
Click here to see image
What I want to get:
Click here to see image
Thanks

Answer 1

When I saw your script, only the 2nd element of rowData is split with ,. I thought that this might be the reason for your issue. And, when appendRow is used in a loop, the process cost will become high. So, in your situation, how about the following modification?
From:
rowData.splice(0, 0, formResponse.getTimestamp());
// Split into different rows afterwards
if (rowData[1].includes(',')) {
rowData[1].split(',').forEach(instanceName => {
let tmpRow = rowData.map(data => data);
tmpRow[1] = instanceName;
sheet.appendRow(tmpRow);
// Append to the sheet
});
}
else {
sheet.appendRow(rowData); // Append to the sheet
}
To:
var date = formResponse.getTimestamp();
var values = rowData.map(v => v.includes(',') ? v.split(",") : [v]);
var res = values[0].map((_, c) => [date, ...values.map(r => r[c] || "")]);
sheet.getRange(sheet.getLastRow() + 1, 1, res.length, res[0].length).setValues(res);
Reference:
map()