nonBoolean
function nonBoolean<T>(value: T | boolean): value is T;
nonBoolean(value) is the same test as !isBoolean(value), written so that a guard clause reads as a sentence rather than as a negation.
Only the two primitives pass. new Boolean(false) is an object, and the strings "true" and "false" are strings.
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 not a boolean; otherwise false.
In TypeScript the guard narrows value to T inside the branch.
Examples
What passes and what does not
nonBoolean("true"); // => true
nonBoolean(1); // => true
nonBoolean(null); // => true
nonBoolean(true); // => false
nonBoolean(false); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.