nonString
function nonString<T>(value: T | string): value is T;
nonString(value) is the same test as !isString(value), written so that a guard clause reads as a sentence rather than as a negation.
The test is typeof value === "string", so the empty string passes and a String object, being an object, does not.
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 string; otherwise false.
In TypeScript the guard narrows value to T inside the branch.
Examples
What passes and what does not
nonString(1); // => true
nonString(null); // => true
nonString([]); // => true
nonString(""); // => false
nonString("abc"); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.