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Finite

finite validates that a number is finite (not Infinity, -Infinity, or NaN).

It enforces strict numeric validation and rejects any non-number value or non-finite number. If the value is not a number or is not finite, the rule emits a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

.finite()

And internally:

export const finite: ValidationRule
(value: unknown, path: FieldPath) => Promise<ReadonlyArray<JaneEvent>>

Events

Event code Description
type.not.valid Value is not structurally a number
number.not.finite Number is Infinity, -Infinity, or NaN

Design rationale

  • Provides a strict, predictable finite number validation.
  • Rejects infinite values and NaN explicitly.
  • Rejects non-number values with a clear structural-type diagnostic.
  • Never coerces or normalizes — validation is explicit and opt-in.
  • Emits exactly one event per failure for clarity and composability.
  • Async-compatible and returns a readonly array of JaneEvent objects.

Invoke

finite runs only when explicitly included in a boundary or pipeline. It does not run automatically.

The rule activates when:

  • The value is any JavaScript value.
  • If the value is not a number, emits type.not.valid.
  • If the value is a number but not finite, emits number.not.finite.
  • If the value is a finite number → returns an empty result set.

Examples

Valid finite number

await finite(42, "$");
// → []

Infinity

await finite(Infinity, "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "number.not.finite",
//       path: "$",
//       ...
//     }
//   ]

Non-number value

await finite("42", "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "type.not.valid",
//       path: "$",
//       ...
//     }
//   ]