Copy cell if certain condition met - if-statement

Question

I know there are already many topics like mine, but I am completely new to programming scripts and therefore I ask you to help me with following problem:
In cell B2 is the user name and in cell C2 the submitter type - if the submitter type is "Requester" then the user name of cell B2 should be copied to cell AE2 - the problem is, that I also want to keep the previous user names if the submitter type change and gets updated...
That means, first the submitter type is "Requester" then the system should copy the user name to cell AE2 - if the submitter type of my line change, then the already copied user name should not change - understood what I want? This should work for all lines of the spreadsheet...
I tried the code but got following error:
Maybe you can improve the code for me?
I changed those 2:
Before:
for (var i = 1; i <= numRows; i++) {
var userNameCell = rows.getCell(i, userNameColumn);
var subTypeCell = rows.getCell(i, subTypeColumn);
var sUserNameCell = rows.getCell(i, sUserNameColumn);
After:
for (var i = 1; i <= numRows; i++) {
var userNameCell = rows.getCell(i, userNameColumn);
var sUserNameCell = rows.getCell(i, sUserNameColumn);
var subTypeCell = rows.getCell(i, subTypeColumn);
The error now is:
new error
Or was the change wrong? Maybe you mean that:
var userNameColumn = 2; //Column where the user name is written
var subTypeColumn = 5; //Column where the submitter type is written ex. "Requester"
var sUserNameColumn = 3; //Column where the user name is saved
But then only one object (username) is known instead of 2 before - subTypeCell and sUserNameCell again undefined - that says the debugger - the code looks now like that (again with my changes, because then 2 objects instead only 1 is known):

Answer 1

You can do something like this:
var userNameColumn = 2; //Column where the user name is written
var subTypeColumn = 3; //Column where the submitter type is written ex. "Requester"
var sUserNameColumn = 5; //Column where the user name is saved
function saveUserName() {
var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheets()[0];
var rows = sheet.getDataRange();
var numRows = rows.getNumRows();
for (var i = 1; i <= numRows; i++) {
var userNameCell = rows.getCell(i, userNameColumn);
var subTypeCell = rows.getCell(i, subTypeColumn);
var sUserNameCell = rows.getCell(i, sUserNameColumn);
if(sUserNameCell.isBlank() && subTypeCell.getValue() === 'Requester') {
sUserNameCell.setValue(userNameCell)
};
}
}
Firstly this defines the columns that you are working with, which are the "Username"(in the scriptuserNameColumn), the column with the "Submitter type"(in the scriptsubTypeColumn) and the column where the username is saved (in the scriptsUserNameColumn). Each have been assigned a number corresponding to a columns in spreadsheet, wher 2 is B, 3 is C, and so on. You can change them to your needs.
Then we create a function called saveUserName() inside this function we get the current spreadsheet, we define what range in the spreadsheet we will work with, here it is everything, then we get the number of rows that has data in them.
After that we go through the data we defined, and setup some variables we can use for each cell. Then we create our if statement, which states, if the "Saved-User-Name-Cell" is empty and the "Submitter-Type-Cell" = the word 'Requester' then we grab the "Saved-User-Name-Cell" and set it's value equal to what is within the "User-Name-Cell".
That's it!