Get or create a sheet by name

Half of Northwind’s “the script broke” reports come down to one thing: a tab was renamed or deleted, and getSheetByName returned null. Reach for this helper instead — it returns the tab if it exists, and creates it on the spot if it doesn’t.

The helper

/**
 * Return a sheet by name, creating it if it does not exist.
 * @param {string} name  The tab name, e.g. 'Invoices'.
 * @param {Spreadsheet} [ss]  Defaults to the active spreadsheet.
 * @return {Sheet} The existing or newly created sheet.
 */
function getOrCreateSheet(name, ss) {
  ss = ss || SpreadsheetApp.getActiveSpreadsheet();
  return ss.getSheetByName(name) || ss.insertSheet(name);
}

Using it

Drop it into any Northwind workbook script and stop null-checking by hand:

function logInvoiceRun() {
  // Always returns a usable sheet — no null, no crash.
  const log = getOrCreateSheet('Invoice Log');
  log.appendRow([new Date(), 'invoices generated']);
}

If you also want fresh headers when the tab is brand new, check the row count:

function getLogSheet() {
  const sheet = getOrCreateSheet('Invoice Log');
  if (sheet.getLastRow() === 0) {
    sheet.appendRow(['timestamp', 'event']); // seed headers once
  }
  return sheet;
}