Complex transpose exceeding run time in Google Apps Script - google-apps-script

Question

I am receiving data in a single column and must transpose that into individual records. Some records will be 12 characters long, others 10, and the remainder 9. Furthermore, the latter 2 values in the 10 and 9-character-long records must be shifted 1 and 2 fields to the right, respectively. The first value in a given record is always a date. I have created the following code which works well, except that it times out after about 6 minutes and 77 records. I need to be able to handle 15 times as many if not more.
I embedded the calculation of the date objects in the else section of each if statement and nested the subsequent if statements in an effort to reduce unnecessary calculations. This got me from about 48 records to 77.
Very grateful for any clever insight 🙂
function transposeNew(){
let ss = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
let lr = ss.getRange("A13").getDataRegion().getLastRow();
let sr = 13
// get the data column
let data = ss.getRange(sr,1,lr-sr,1).getValues();
// set up the rows loop
let pasteRow = 2;
let arrayField = 0;
while (arrayField < data.length){
//use the new Date() constructor to create a date object with the date value passed
let isDate12 = new Date(data[arrayField+12]).getFullYear(); //processed; size input;record should include 12 rows & 13th should be a date to begin the next row
if (isDate12 === 2020) {
let record = data.slice(arrayField, arrayField+12);
let recordTr = transposeSub(record);
ss.getRange(pasteRow, 5, 1, 12).setValues(recordTr);
arrayField = arrayField + 12;
}
else {
let isDate10 = new Date(data[arrayField+10]).getFullYear(); //unprocessed;size input
if (isDate10 === 2020) {
let record = data.slice(arrayField, arrayField+10);
let record1 = record.slice(0,8);
let record1Tr = transposeSub(record1);
let record2 = record.slice(8,10);
let record2Tr = transposeSub(record2);
ss.getRange(pasteRow, 5, 1, 8).setValues(record1Tr);
ss.getRange(pasteRow, 14, 1, 2).setValues(record2Tr);
arrayField = arrayField + 10;
}
else {
let isDate9 = new Date(data[arrayField+9]).getFullYear(); //unprocessed;no size
input
if (isDate9 === 2020) {
let record = data.slice(arrayField, arrayField+10);
let record1 = record.slice(0,7);
let record1Tr = transposeSub(record1);
let record2 = record.slice(7,9);
let record2Tr = transposeSub(record2);
ss.getRange(pasteRow, 5, 1, 7).setValues(record1Tr);
ss.getRange(pasteRow, 14, 1, 2).setValues(record2Tr);
arrayField = arrayField + 9;
}
}
}
pasteRow ++;
}
}
function transposeSub(a)
{
return Object.keys(a[0]).map(function (c) { return a.map(function (r) { return r[c]; }); });
}

Answer 1

I see you create a loop and inside this while statement you call several times to SpreadsheetApp functions. This creates a connection to the spreadsheet, reads/changes its data and close connection a lot of times, that's why your code is taking too long to run. Please check GAS Best Practices batch operations section.
You should consider banishing any get/setValue() inside while, instead, call getValues() to hold all values in a javascript array before while and then use setValues() after while to write all outputs at once. The described concept is explored in this answer.

Answer 2

So it turns out that the problem was a flaw in the loop criteria; rookie mistake. There was a data anomaly such that one record did not meet the criteria in any of the if statements and so the loop was continuing in perpetuity. I discovered this by inserting the values for pasteRow and arrayField next to each record on the sheet so that I could see where it was breaking. Interestingly, the records stopped, but the pasteRow and arrayField values continued into the 20,000s before the app quit.
I do note that the feedback provided by #Bruno Polo and #Cooper are correct. Shortly after posting this I reworked it to push the records into a new array and paste the array once complete. That failed due to the same reason noted above. I think I will go back to that version now that I understand the problem.
Thank you for looking at this with me. This is an extraordinary community of experts from whom I have learned so much! 😁