requireTextOutput

function requireTextOutput(
  value: unknown,
  message: string = "Expected a TextOutput object."
): 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
`value`	`unknown`	The value to validate.
`message` (optional) `= "Expected a TextOutput object."`	`string`	The message of the exception. A default is used when omitted.

Returns

TextOutput — the same value, typed as a TextOutput.

Throws

Exception	Condition
`IllegalArgumentException`	the value is not a TextOutput.

Examples

What passes and what does not

const output = ContentService.createTextOutput("hi");

requireTextOutput(output); // => output
requireTextOutput({}); // throws IllegalArgumentException
requireTextOutput(null); // throws IllegalArgumentException

Source

src/appsscript/ui/requireTextOutput.ts

23 September 2026

This documentation was generated with AI (Claude) from the library's source code.

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