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Is email

isEmail validates that a value is a general‑purpose email address.

It uses a permissive but reliable pattern suitable for everyday user input. The rule ensures the value resembles a conventional email address without enforcing strict RFC semantics. Any non‑string value or string that fails the pattern results in a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

.isEmail();

And internally:

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

Events

Event code Description
type.not.valid Value is not a string.
string.not.email String does not match the general pattern.

Design rationale

  • Provides a permissive, user‑friendly email validator appropriate for common forms and input fields.
  • Rejects non‑string values early with a structural‑type diagnostic.
  • Uses a simple, well‑established pattern: /^[^\s@]+@[^\s@]+\.[^\s@]+$/.
  • Avoids strict RFC enforcement — contributors should use isEmailStrict when needed.
  • 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

isEmail 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 string does not match /^[^\s@]+@[^\s@]+\.[^\s@]+$/, emits string.not.email.
  • Otherwise, returns an empty result set.

Examples

Valid — general‑purpose email addresses

await isEmail("user@example.com", "$");
// → []

await isEmail("john.doe+tag@domain.co", "$");
// → []

Invalid — non‑string values

await isEmail(123, "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "type.not.valid",
//       path: "$",
//       ...
//     }
//   ]

Invalid — incorrect format

await isEmail("user@", "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.email",
//       path: "$",
//       ...
//     }
//   ]


await isEmail("user@domain", "$"); // missing TLD
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.email",
//       path: "$",
//       ...
//     }
//   ]