google sheets - Help in limiting script to apply on specific range

function hideRows() {
  var sheet = SpreadsheetApp.getActive().getSheetByName("Sheet1");
  var data = sheet.getDataRange().getValues();
  for(var i = 1; i < data.length; i++) 
 { 
  if(data[i][0] !== "EFG")
    {sheet.showRows(i + 1);}
  if(data[i][0] === "EFG")
    {sheet.hideRows(i + 1);}
  }
}

Need help in limiting this to APPLY to A2:A20 ONLY