google script get sheet size

                                    //getRange(row, column, optNumRows, optNumColumns);
Sheet.getRange(1,1,1,12);

//row --- int --- top row of the range
//column --- int--- leftmost column of the range
//optNumRows --- int --- number of rows in the range.
//optNumColumns --- int --- number of columns in the range

                                    // This example assumes there is a sheet named "first"
var ss = SpreadsheetApp.getActiveSpreadsheet();
var first = ss.getSheetByName("first");
Logger.log(first.getMaxColumns());
// getMaxColumns() returns the current number of columns in the sheet,
// regardless of content.