How to make autocomplete script?

Question

Google Apps Script

There is a table consisting of a fixed number of columns, the number of rows is constantly changing (say columns A,B,C,D). If I manually add information to column A in a new row (thereby expanding the table), then columns B and D in the same row should be filled with a script (there are formulas in these columns, respectively, formulas should be passed to them). How to implement it?

Answer 1

https://stackoverflow.com/questions/12036726/how-d...
https://stackoverflow.com/questions/38287554/googl...

Answer 2

Much can be done purely by formulas. Here is an example - if there is something in column A , then the sum ( A + B ) is obtained. Write it down in C1 and add values ​​to A and B.

=arrayFormula(
  еслиошибка(
     если(a:a<>""; a:a+b:b; "")
  )
)

Demo table