isString
function isString(value: unknown): value is string;
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 a string; otherwise false.
In TypeScript the guard narrows value to string inside the branch.
Examples
What passes and what does not
isString(""); // => true
isString("abc"); // => true
isString(1); // => false
isString(null); // => false
isString([]); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.