API reference › @evolu/common › Type › identifier

function identifier<Casing>(
  casing: Casing,
): BrandFactory<
  IdentifierBrandByCasing[Casing],
  string,
  IdentifierError<Casing>
>;

Defined in: packages/common/src/Type.ts:5694

Adds identifier validation in a naming convention to an existing string Type.

An identifier is one or more ASCII words, each starting with a letter and continuing with letters or digits. camelCase and PascalCase start every word after the first with an uppercase letter, so httpUrl has two words and httpURL has four. snake_case, kebab-case, and CONSTANT_CASE put exactly one separator between words. Validation keeps the spelling and rejects empty strings, whitespace, punctuation, and non-ASCII characters.

Words never start with a digit. Identifier grammars in most languages forbid a leading digit, and camelCase cannot mark a word boundary before one, so the rule applies to every word and keeps every conversion exact. Join an abbreviation such as 2FA to the previous word, as in MAX2FA_ATTEMPTS and max2faAttempts, or spell the number out, as in TWO_FACTOR_SECRET.

Convert validated identifiers with functions such as camelCaseToSnakeCase. Conversions preserve word boundaries, and converting back restores the original spelling. They return only the destination brand, dropping unrelated constraints such as input length.

Example

import {
  assertErr,
  assertOk,
  identifier,
  maxLength,
  String,
} from "@evolu/common";

const EnvName = identifier("CONSTANT_CASE")(maxLength(16)(String));

assertOk(EnvName.fromUnknown("HTTP2_PORT"), "HTTP2_PORT");
assertErr(EnvName.fromUnknown("HTTP_2_PORT"));