requireInteger

function requireInteger(value: unknown, message: string = "Expected an integer."): 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
`value`	`unknown`	The value to validate.
`message` (optional) `= "Expected an integer."`	`string`	The message of the exception. A default is used when omitted.

Returns

number — the same value, typed as an integer.

Throws

Exception	Condition
`IllegalArgumentException`	the value is not an integer.

Examples

What passes and what does not

requireInteger(42); // => 42
requireInteger(-7); // => -7
requireInteger(1.5); // throws IllegalArgumentException
requireInteger(NaN); // throws IllegalArgumentException

Source

src/lang/number/requireInteger.ts

23 September 2026

This documentation was generated with AI (Claude) from the library's source code.

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