I am trying to perform a similar VLOOKUP as described in this

CodePudding user response：

I think I've resolved the issue. There may be a better way but this works for now.

function updateMaster() {
  const mss = SpreadsheetApp.getActiveSpreadsheet();
  const msh = mss.getSheetByName('Data');
  const mDB = msh.getRange("A2:A"   msh.getLastRow()).getValues(); //Gets ID's from Master Spreadsheet

  var combinedData = [];   // edited

  const ish = mss.getSheetByName('Sheet IDs'); 
  const ivs = ish.getRange('A1:A'   ish.getLastRow()).getValues().flat(); 
  ivs.forEach((id,i) => {
    let ss = SpreadsheetApp.openById(id);
    let sh = ss.getSheetByName('Sep 22');
    let vs = sh.getRange("A2:L"   sh.getLastRow()).getValues();  //Get's ID's from individual sheets
    combinedData = combinedData.concat(vs);  // edited
    Logger.log(combinedData)

  // Create an object for searching the values of column "A".
  const obj = combinedData.reduce((o, [a,,,,,,,,,, ...kl]) => ((o[a] = kl), o), {});
  
  // Create an array for putting to the Spreadsheet.
  const values = mDB.map(([g]) => obj[g] || ["", ""]);

  // Put the array to the Spreadsheet.
  msh.getRange(2, 7, values.length, 2).setValues(values);
    });
}