How to get Error Message from a Google sheet cell using Google Apps Script?

I am trying to extract the error message from "A2" cell of Google sheet using the spreadsheets.get Sheets v4 API method. I fond this demo and modified the code to the snippet below. However it does not give the required output:

function getErrorMessage(){
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheetByName("Sheet1");

  const value = sheet.getRange("A2").getDisplayValue();
  Logger.log(value);
  if (value == "#REF!") {
    const obj = Sheets.Spreadsheets.get(ss.getId(), {
      ranges: [sheet.getSheetName()],
      fields: "sheets",
    });
    const v = obj.sheets[0].data[0].rowData[0].values[0];
    
    if (
      v.hasOwnProperty("effectiveValue") &&
      v.effectiveValue.hasOwnProperty("errorValue")
    ) {
      res.error = v.effectiveValue.errorValue;
      Logger.log(res.error);
    }
  }
}

The error in cell "A2" looks like this:

I want to get the text saying:
> Result was not automatically expanded, please insert more rows (1655).

Any guidance would be much appreciated.

In your showing script, it seems that res is not declared. So, how about the following modification?

From:

res.error = v.effectiveValue.errorValue;
Logger.log(res.error);

To:

const error = v.effectiveValue.errorValue;
Logger.log(error);

Note:

• As a test, when I put a formula of =A2 into a cell "A2, and run the script by reflecting my proposed modification, Logger.log(error); showed Circular dependency detected. To resolve with iterative calculation, see File > Settings. in the log.

Added:

From your reply, how about the following modification? In this modification, the cell coordinate is directly used.

function getErrorMessage() {
  const a1Notation = "'Sheet1'!A2";

  var ss = SpreadsheetApp.getActiveSpreadsheet();
  const value = ss.getRange(a1Notation).getDisplayValue();
  Logger.log(value);
  if (value == "#REF!") {
    Logger.log("I'm in")
    const obj = Sheets.Spreadsheets.get(ss.getId(), {
      ranges: [a1Notation],
      fields: "sheets(data(rowData(values(effectiveValue(errorValue)))))",
    });
    const v = obj.sheets[0].data[0].rowData[0].values[0];
    if (
      v.hasOwnProperty("effectiveValue") &&
      v.effectiveValue.hasOwnProperty("errorValue")
    ) {
      const error = v.effectiveValue.errorValue;
      Logger.log(error);
    }
  }
}