Trimmed¶

trimmed validates that a string contains no leading or trailing whitespace.

It enforces strict structural string validation and rejects any non-string value or string that differs from its trimmed version. If the value is not a string or has leading/trailing whitespace, the rule emits a single validation event. Otherwise, it produces no validation output.

Signature¶

Through the API:

.trimmed()

And internally:

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

Events¶

Event code	Description
`type.not.valid`	Value is not structurally a string
`string.not.trimmed`	String has leading or trailing whitespace

Design rationale¶

Provides a strict, predictable whitespace edge validation.
Rejects non-string 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¶

trimmed 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 string, emits type.not.valid.
If the value is a string but has leading/trailing whitespace, emits string.not.trimmed.
If the value is a string with no leading/trailing whitespace → returns an empty result set.

Examples¶

Valid trimmed string¶

await trimmed("hello", "$");
// → []

String with leading whitespace¶

await trimmed("  hello", "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.trimmed",
//       path: "$",
//       ...
//     }
//   ]

Non-string value¶

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