isInteger
function isInteger(value: unknown): value is number;
A number with no fractional part. Nothing is coerced, so the string "42" is not an integer, and NaN is not either.
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 an integer; otherwise false.
In TypeScript the guard narrows value to number inside the branch.
Examples
What passes and what does not
isInteger(42); // => true
isInteger(-7); // => true
isInteger(0); // => true
isInteger(1.5); // => false
isInteger(NaN); // => false
isInteger("42"); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.