Stacking Columnar Data Into Rows Using App Script or Node JS - node.js

Question

I have data which users submit in columns. I am trying to convert them from columnar into stacked rows so a database can read them as single columns, rather than having to pull in X columns to capture the data.
You can see in the Columnar Example screenshot where I am presently, and in the Stacked Example where I want to be.
I can do this in either Google Sheets using App Script - load the data as columnar then convert to stacked and move to BigQuery - OR - use Google Cloud Storage to load the columnar data then use Node to convert to stacked when moving to BigQuery.
Either way, this needs to get into BigQuery as the Stacked Example.
Any ideas on how to do this?

Answer 1

The function below does the following:
Get all data from the sheet where your original data is located (called Source, please change accordingly) with getDataRange.
Remove the headers from the retrieved array and append them to your destination sheet (called Target) with shift, slice and appendRow.
Iterate through the rest of rows with a forEach and, for each row, iterate through each successive group of four columns with a for loop, appending (1) the first for columns of each row and (2) each successive group of four columns in a new row in your destination sheet.
function myFunction() {
var ss = SpreadsheetApp.getActive();
var sourceSheet = ss.getSheetByName('Source'); // Change accordingly
var targetSheet = ss.getSheetByName('Target'); // Change accordingly
targetSheet.clearContents(); // Removes all old content from target sheet before appending new data (remove this if you don't want that)
var sourceValues = sourceSheet.getDataRange().getValues();
var numCols = 4; // Number of desired columns in destination spreadsheet
var headers = sourceValues.shift().slice(0, numCols * 2);
targetSheet.appendRow(headers); // Remove if the destination sheet already has headers
sourceValues.forEach(function(row) { // Iterate through each row in source sheet
for (var i = numCols; i < row.length; i += numCols) { // Iterate through each group of four columns (excluding first four) in each row
var part1 = row.slice(0, numCols); // First four columns
var part2 = row.slice(i, i + numCols); // Each successive group of four
var targetRow = part1.concat(part2); // Concatenate the four first columns with each group of four
targetSheet.appendRow(targetRow); // Append row (8 columns)
}
});
}