requireFloat

function requireFloat(
  value: unknown,
  message: string = "Expected a number with a fractional part."
): number;

JavaScript has one numeric type, so 1.0 and 1 are the same value: the question answered is whether a fraction survives at runtime, not how the literal was written. The infinities have no fraction and are excluded.

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 a number with a fractional part."`	`string`	The message of the exception. A default is used when omitted.

Returns

number — the same value, typed as a number with a fractional part.

Throws

Exception	Condition
`IllegalArgumentException`	the value is not a number with a fractional part.

Examples

What passes and what does not

requireFloat(1.5); // => 1.5
requireFloat(-0.1); // => -0.1
requireFloat(42); // throws IllegalArgumentException
requireFloat(1.0); // throws IllegalArgumentException

Source

src/lang/number/requireFloat.ts

23 September 2026

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

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