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Min keys

minKeys validates that a plain object contains at least a specified minimum number of own enumerable keys.

It performs a strict structural check ensuring the value is a plain object, then validates that it has at least the required number of keys. If the value is not a plain object or has too few keys, the rule emits a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

.minKeys(minimum: number)

And internally:

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

Events

Event code Description
object.not.plain-object Value is not a JSON-compatible plain object
object.too.few-keys Object contains fewer than the minimum required keys

Design rationale

  • Provides a strict, predictable minimum key count validation.
  • First ensures the value is a plain object, then checks key count.
  • Counts only own enumerable keys using Object.keys().
  • 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

minKeys 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 plain object, emits object.not.plain-object.
  • If the value is a plain object but has fewer than the minimum keys, emits object.too.few-keys.
  • If the value is a plain object with at least the minimum keys → returns an empty result set.

Examples

Valid object with minimum keys

await minKeys(2)({ name: "John", age: 30, city: "NYC" }, "$");
// → []

Object with too few keys

await minKeys(2)({ name: "John" }, "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "object.too.few-keys",
//       path: "$",
//       ...
//     }
//   ]

Array (invalid)

await minKeys(2)([1, 2, 3], "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "object.not.plain-object",
//       path: "$",
//       ...
//     }
//   ]