isTextOutput
function isTextOutput(value: unknown): value is TextOutput;
An Apps Script service object has no constructor a script can test against, so the guard looks for the methods that define the type — getMimeType, getContent. A stub that implements them passes, which is what makes code using this guard testable outside the runtime.
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 TextOutput; otherwise false.
In TypeScript the guard narrows value to TextOutput inside the branch.
Examples
What passes and what does not
const output = ContentService.createTextOutput("hi");
isTextOutput(output); // => true
isTextOutput({}); // => false
isTextOutput(null); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.