isNil
function isNil(value: unknown): value is null | undefined;
The absent values, and only those: 0, "" and false are present values and do not qualify.
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 null or undefined; otherwise false.
In TypeScript the guard narrows value to null | undefined inside the branch.
Examples
What passes and what does not
isNil(null); // => true
isNil(undefined); // => true
isNil(0); // => false
isNil(""); // => false
isNil(false); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.