Using for and if loops in Google Apps Script - google-apps-script

Question

Dear programming Community,
at first I need to state, that I am not quite experienced in VBA and programming in general.
What is my problem? I have created a topic list in google sheets in order to collect topics for our monthly meeting among members in a little dance club. That list has a few columns (A: date of creation of topic; B: topic; C: Name of creator; ...). Since it is hard to force all the people to use the same format for the date (column A; some use the year, others not, ...), I decided to lock the entire column A (read-only) and put a formular there in all cells that looks in the adjacent cell in column B and sets the current date, if someone types in a new topic (=if(B2="";"";Now()). Here the problem is, that google sheets (and excel) does then always update the date, when you open the file a few days later again. I tried to overcome this problem by using a circular reference, but that doesn't work either. So now I am thinking of creating a little function (macro) that gets triggered when the file is closed.
Every cell in Column B (Topic) in the range from row 2 to 1000 (row 1 is headline) shall be checked if someone created a new topic (whether or not its empty). If it is not empty, the Date in the adjacent cell (Column A) shall be copied and reinserted just as the value (to get rid of the formular in that cell). Since it also can happen, that someone has created a topic, but a few days later decides to delete it again, in that case the formular for the date shall be inserted again. I thought to solve this with an If-Then-Else loop (If B is not empty, then copy/paste A, else insert formula in A) in a For loop (checking rows 1 - 1000). This is what I have so far, but unfortunately does not work. Could someone help me out here?
Thanks in advance and best regards,
Harry
function NeuerTest () {
var ss=SpreadsheetApp.getActive();
var s=ss.getSheetByName('Themenspeicher');
var thema = s.getCell(i,2);
var datum = s.getCell(i,1);
for (i=2;i<=100;i++) {
if(thema.isBlank){
}
else {
datum.copyTo(spreadsheet.getActiveRange(), SpreadsheetApp.CopyPasteType.PASTE_VALUES, false);
}}
}

Answer 1

The suggested approach is to limit the calls to the Spreadsheet API, therefore instead of getting every cell, get all the data at once.
// this gets all the data in the Sheet
const allRows = s.getDataRange().getValues()
// here we will store what is written back into the sheet
const output = []
// now go through each row
allRows.forEach( (row, ind) => {
const currentRowNumber = ind+1
// check if column b is empty
if( !row[1] || row[1]= "" ){
// it is, therefore add a row with a formula
output.push( ["=YOUR_FORMULA_HERE"] )
} else {
// keep the existing value
output.push( [row[0]] )
}
})

Answer 2

Basically it could be something like this:
function myFunction() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName('Themenspeicher');
var range = sheet.getRange('A2:B1000');
var data = range.getValues(); // <---- or: range.getDisplayValues();
for (let row in data) {
var formula = '=if(B' + (+row+2) + '="";"";Now())';
if (data[row][1] == '') data[row][0] = formula;
}
range.setValues(data);
}
But actual answer depends on what exactly you have, how your formula looks like, etc. It would be better if you show a sample of your sheet (a couple of screenshots would be enough) 'before the script' and 'after the script'.