Error in jS When importing csv into mysql database?

Question

PHP

I decided to use a ready-made script for importing csv into mysql,
but in one of the files it gives an error
TypeError: combo3.attachEvent is not a function
dviglo-shop.loc/csv_importer/includes/javascript/s...
Line 82

function CreateForm_existing() {
  doc.form1.stage.value = "import_setup";

  // Empty workarea
  EmptyWorkarea(div);
  
  var workarea = doc.getElementById(div);
  
  // Declare vars
  var freeVar;
  var i;
  var a_href;
  
  var table = _table.cloneNode(true);  // Create table
  var tbody = _tbody.cloneNode(false);  // Create tbody
  
  var row1 = _tr.cloneNode(false);	// Row for database
  var cell11 = _td.cloneNode(false);	// Cell for words
  var cell12 = _td.cloneNode(false);	// Cell for combo
  
  var text1 = doc.createTextNode("Select database: ");
  var combo3 = _select.cloneNode(false);	// SELECT control for database
    combo3.setAttribute("name", "dvigloshop");
  combo3.attachEvent("onchange", GetTables);
  combo3.options[combo3.length] = new Option("Select database", "");  // Add "Select database option"

  for (i = 0; i < mysqlDatabaseArray.length; i++) {
    combo3.options[combo3.length] = new Option(mysqlDatabaseArray[i], mysqlDatabaseArray[i]);  // Add databases to options of SELECT control
  }
  
  row2 = _tr.cloneNode(false);	// Row for tables
  cell21 = _td.cloneNode(false);	// Cell for word
  cell22 = _td.cloneNode(false);	// Cell for combo
  
  var text2 = doc.createTextNode("Select table: ");
  var combo2 = _select.cloneNode(false);	// SELECT control for tables
    combo2.setAttribute("name", "dbTableName");
  
  
  workarea.appendChild(table);
  table.appendChild(tbody);
  
  tbody.appendChild(row1);
    row1.appendChild(cell11);
      cell11.appendChild(text1);
    row1.appendChild(cell12);
      cell12.appendChild(combo3);
  
  tbody.appendChild(row2);
    row2.appendChild(cell21);
      cell21.appendChild(text2);
    row2.appendChild(cell22);
      cell22.appendChild(combo2);
  
  combo3.focus();
}
function GetTables() {
  var cmbTable = FieldSearch(doc.form1, "dbTableName");
  var cmbDatabase = FieldSearch(doc.form1, "dbName");
  var db = cmbDatabase.value;

  for (i = cmbTable.length; i >= 0; i--) {
    cmbTable.options[i] = null;
  }

  cmbTable.options[0] = new Option("Select table", "");

  for (i = 0; i < mysqlTableArray[db].length; i++) {
    cmbTable.options[(i+1)] = new Option(mysqlTableArray[db][i], mysqlTableArray[db][i]);
  }

  cmbTable.focus();
}