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Not before

notBefore validates that a Date instance is not before the specified minimum boundary (inclusive comparison).

It performs a strict type check ensuring the value is a valid Date instance, then validates that the timestamp is greater than or equal to the minimum boundary. If the value is not a Date, is invalid, or is before the minimum, the rule emits a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

.notBefore(min: Date)

And internally:

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

Events

Event code Description
date.not.date Value is not a Date instance
date.is.invalid Date instance represents an invalid date
date.too.early Date is before the minimum boundary

Design rationale

  • Provides a strict, predictable minimum date boundary validation.
  • First ensures the value is a valid Date instance.
  • Then validates the timestamp is ≥ the minimum boundary.
  • Inclusive comparison allows exact boundary matches.
  • 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

notBefore 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 Date instance, emits date.not.date.
  • If the value is a Date but invalid, emits date.is.invalid.
  • If the value is a valid Date but before the minimum, emits date.too.early.
  • If the value is a valid Date ≥ minimum boundary → returns an empty result set.

Examples

Date at minimum boundary

const minDate = new Date("2023-01-01");
await notBefore(minDate)(new Date("2023-01-01"), "$");
// → []

Date before minimum

const minDate = new Date("2023-01-01");
await notBefore(minDate)(new Date("2022-12-31"), "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "date.too.early",
//       path: "$",
//       ...
//     }
//   ]

Non-Date value

const minDate = new Date("2023-01-01");
await notBefore(minDate)("2023-01-01", "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "date.not.date",
//       path: "$",
//       ...
//     }
//   ]