isCountable
function isCountable(value: unknown): value is number;
A value that can serve as a quantity, a length or a zero-based index: a whole number, not negative, and small enough that integer arithmetic on it is still exact.
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 countable number; otherwise false.
In TypeScript the guard narrows value to number inside the branch.
Examples
What passes and what does not
isCountable(0); // => true
isCountable(42); // => true
isCountable(-1); // => false
isCountable(1.5); // => false
isCountable(Number.MAX_SAFE_INTEGER + 2); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.