Google-sheets – Remove word values from the output of UNIQUE(SourceArray) in a Google spreadsheet

Instead of using a script, consider to add the responses to another sheet using formulas and there add the three columns.

It's worth to say that Today() column will be updated when the recalculation occurs.

I.E. Adding a column with the formula =Today() to the responses of a form add the following formula to A1 in a new sheet:

=ArrayFormula(
{
filter(Sheet1!A:B,Sheet1!A:A<>""),
transpose(
split(
rept(
Today()&char(9),
countif(Sheet1!A:A,"<>")
),
char(9)
)
)
}
)

This can be done with the following script: set a trigger "on form submit" for this function.

The customizable parameters are: the column number where to insert Id, and the initial Id. The function uses Script Properties to keep track of the used Id, so they will not be repeated.

function generateId(e) {
  var columnNumber = 5;
  var initialId = 42;
  var sp = PropertiesService.getScriptProperties();
  var id = sp.getProperty("Event Id") || initialId;
  e.range.offset(0, columnNumber - 1, 1, 1).setValue(id);
  sp.setProperty("Event Id", id + 1);
}