isSheet
function isSheet(value: unknown): value is GoogleAppsScript.Spreadsheet.Sheet;
An Apps Script service object has no constructor a script can test against, so the guard reads the tag the object reports for itself: value.toString() === "Sheet". A plain object that reports the same tag passes too, which in practice means a test double.
isX and nonX answer a question and never interrupt control flow; requireX and requireNonX hand the value back or throw. The scheme is explained in Validation conventions.
Parameters
Parameter | Type | Description |
|---|---|---|
|
| The value to check. |
Returns
boolean — true when the value is a sheet; otherwise false.
In TypeScript the guard narrows value to GoogleAppsScript.Spreadsheet.Sheet inside the branch.
Examples
What passes and what does not
const sheet = SpreadsheetApp.getActiveSheet();
isSheet(sheet); // => true
isSheet({}); // => false
isSheet(null); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.