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Is UUID

isUuid validates that a value is a UUID in canonical hyphenated form for versions 1–4.

It enforces strict structural and bit‑level requirements: the value must be a string, must follow the canonical 8‑4‑4‑4‑12 hyphenated layout, must contain only hexadecimal characters, must specify a version between 1 and 4, and must use a valid variant nibble. Any non‑string value or incorrectly formatted UUID results in a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

isUuid();

And internally:

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

Events

Event code Description
type.not.valid Value is not a string.
string.not.uuid String does not match UUID v1–v4 canonical form.

Design rationale

  • Enforces canonical UUID formatting: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
  • Restricts version nibble to 1–4, matching the validator’s stated scope.
  • Ensures variant nibble is one of 8, 9, a, or b (RFC‑compliant).
  • Rejects non‑string values early with a structural‑type diagnostic.
  • Avoids normalization — contributors must provide canonical UUID strings.
  • Emits exactly one event per failure for clarity and composability.
  • Pure, total, async‑compatible, and returns a readonly array of JaneEvent objects.
  • Preserves the provided path and supports pipeline‑level userMessage overrides.

Invoke

isUuid runs only when explicitly included in a boundary or pipeline. It does not run automatically and is disabled when strict mode is enabled.

The rule activates when:

  • The value is any JavaScript value.
  • If the value is not a string, emits type.not.valid.
  • If the string does not match: /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-4][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/, emits string.not.uuid.
  • Otherwise, returns an empty result set.

Examples

Valid — UUIDs v1–v4

await isUuid("550e8400-e29b-41d4-a716-446655440000", "$");
// → []

await isUuid("f47ac10b-58cc-11cf-a937-08002b1f003d", "$");
// → []

Invalid — non‑string values

await isUuid(12345, "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "type.not.valid",
//       path: "$",
//       ...
//     }
//   ]

Invalid — incorrect format or version

await isUuid("550e8400e29b41d4a716446655440000", "$"); // missing hyphens
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.uuid",
//       path: "$",
//       ...
//     }
//   ]


await isUuid("550e8400-e29b-61d4-a716-446655440000", "$"); // version 6 not allowed
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.uuid",
//       path: "$",
//       ...
//     }
//   ]