Create a TextItem for each product in a spreadsheet and to set the title of this item as "(Name of the product) (remains : (number remaining))" - google-apps-script

Question

I want to make a Google Form for online order which would display the number of remaining units for each product, updated every time an order is passed.
As a first step, I try to create a TextItem for each product in a spreadsheet and to set the title of this item as "(Name of the product) (remains : (number remaining))"
var wsStocks = SpreadsheetApp.openById(ssID).getSheetByName("Stocks");
var form = FormApp.openById(formID);
function myFunction(){
var Products = wsStocks.getRange(1,1,wsStocks.getLastRow(),1).getValues();
for(j=1;j<Products .length+1;j++){
form.addTextItem().setTitle(wsStocks.getRange(j,1).getValue().toString()+" (remains: "+wsStocks.getRange(j,2).getValue().toString()+")");
};
}
When I run the code, the correct number of items are created, but the title seems to be attributed randomly: sometimes it is the expected title, sometimes it remains blank ("Question"). If I run several times the code, the distribution of correct and blank titles changes (sometimes the first and fourth are correct, the other ones are blank, sometimes it's just the second...)
I can check with Logger.log that "Products" does contain the list of products' names, and that the expression given as argument to SetTitle is indeed what I expect. I have no clue what's going on : /

Answer 1

Explanation / Issue:
It is not a good practice to use getRange and getValue within a for loop. You can construct the 2D array Products to include both column A and B and then you can just index both columns directly. I also used template literals to simplify your string expression:
var Products = wsStocks.getRange(1,1,wsStocks.getLastRow(),2).getValues();
for(j=0;j<Products.length;j++){
form.addTextItem().setTitle( `${Products[j][0]} (remains: ${Products[j][1]})` );
};
To answer your question, the issue with your current solution is that you are iteratively adding questions and setting their titles. However, this process needs some time to be completed and the for loop is always faster. You just need to slow down the requests.
Unlike SpreadsheetApp, FormApp does not support the flush method. But there is a workaround which you can use to slow down the requests and that is the sleep method. Of course, this approach will overall slow down your algorithm and if you specify a big enough time interval, your script might not be able to finish in time.
You need to choose the time interval wisely. In the following example, I used 4 seconds, but feel free to try a smaller or bigger time interval depending on the number of requests you need to process. For example, if you still see that you are getting wrong titles, increase that number.
Solution / Workaround:
var wsStocks = SpreadsheetApp.openById(ssID).getSheetByName("Stocks");
var form = FormApp.openById(formID);
function myFunction(){
var Products = wsStocks.getRange(1,1,wsStocks.getLastRow(),2).getValues();
for(j=0;j<Products.length;j++){
form.addTextItem().setTitle( `${Products[j][0]} (remains: ${Products[j][1]})` );
Utilities.sleep(4*1000); // 4 second delay
};
}