isHtmlOutput
function isHtmlOutput(value: unknown): value is HtmlOutput;
An Apps Script service object has no constructor a script can test against, so the guard looks for the methods that define the type — getContent, setTitle, setXFrameOptionsMode. 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 an HtmlOutput; otherwise false.
In TypeScript the guard narrows value to HtmlOutput inside the branch.
Examples
What passes and what does not
const output = HtmlService.createHtmlOutput("<p>hi</p>");
isHtmlOutput(output); // => true
isHtmlOutput({}); // => false
isHtmlOutput(null); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.