Decorators

Validates that an array property contains no more than the given number of elements.

Validates that an array property contains at least the given number of elements.

Validates that an array property contains only unique values.

Creates a property decorator for a validation rule.

The returned factory is callable (VerifyIsEmail() / VerifyMaxLength(255)) and also exposes a .check() predicate for ad-hoc use:

VerifyIsEmail.check('foo@bar.com');       // true
VerifyMaxLength.check('abc', 255);         // true

Usage:

// No options:
export const VerifyIsString = registerRule<void>({
    name: 'IsString',
    check: (value) => typeof value === 'string',
    defaultMessage: ({ property }) => `${property} must be a string`,
});

// With options:
export const VerifyMaxLength = registerRule<number>({
    name: 'MaxLength',
    check: (value, max) =>
        typeof value === 'string' && value.length <= max,
    defaultMessage: ({ property, options }) =>
        `${property} must be at most ${options} characters`,
});

// Array-level:
export const VerifyArrayMinSize = registerRule<number>({
    name: 'ArrayMinSize',
    operatesOn: 'array',
    check: (value, min) => Array.isArray(value) && value.length >= min,
    defaultMessage: ({ property, options }) =>
        `${property} must contain at least ${options} elements`,
});

Validates that the property is an array.

Validates that the property is a boolean.

Validates that a value is a real ISO 3166-1 country code. Membership is checked against the complete list (249 entries per format).

Formats:

• 'alpha2' (default) — two uppercase letters (US, DE, GB)
• 'alpha3' — three uppercase letters (USA, DEU, GBR)
• 'numeric' — three digits as a string, zero-padded (840, 276, 826)

The ISO list is stable (1–2 updates per decade); the embedded data lives in ./internal/Iso3166Codes.ts and can be resynced from the ISO Maintenance Agency when needed.

Validates that the property is a valid Date instance.

Validates that the property is neither null nor undefined.

Validates that the property is a domain name such as example.com or api.example.co.uk.

Validates that the property is a plausible email address. Pragmatic rather than strictly RFC 5322 — layer VerifyStringMatches or VerifyBy for stricter needs.

Validates that a value is one of a defined enumeration.

"Enumeration" here is the general sense — any fixed set of allowed values — not strictly a TypeScript enum. Accepts:

• A TypeScript enum: @VerifyIsEnum(Status)
• A const object: @VerifyIsEnum({ A: 'a', B: 'b' } as const)
• A plain array: @VerifyIsEnum(['Contact', 'Article'])

Validates that the property is an integer.

Validates that the property is an IPv4 or IPv6 address. Pass a version to accept only one family.

Validates that a value is a well-formed BCP 47 language tag.

Uses the built-in Intl.Locale constructor, which parses the full BCP 47 grammar (language, script, region, variants, extensions). Examples that pass: "en", "en-US", "zh-Hans-CN", "ja-JP-u-ca-japanese". Examples that fail: "not-a-locale", "english", "en_US" (underscore).

This is real validation — the runtime does the parsing, so there's no shipped allowlist to maintain.

Validates that the property is not empty — rejects null, undefined, '', [], and {}. Numbers (including 0), booleans, and class instances are never empty.

Validates that the property is a finite number.

Validates that the property is an object (not an array and not null).

Marks the property as optional. When the value is null or undefined, every other rule on the property is skipped.

The rule itself always passes — it serves as a sentinel read by the ValidationEngine.

Standalone validator — exposed for callers that need to run the phone-number check outside a decorator (e.g. in a service method).

Validates that the property is a phone number in an accepted format (E.164 and North American formats by default).

Validates that the property is a string.

Validates that the property is a valid IANA time zone name such as America/Denver.

Validates that the property is a valid http: or https: URL.

Validates that the property is a UUID of the given version (1–8, or 'all' for any version).

Validates that a string or array property's length is at least min and, when given, at most max (inclusive).

Validates that a number property is not greater than the given maximum.

Validates that a Date property is on or before the given maximum.

Validates that a string or array property is at most the given length.

Validates that a number property is not less than the given minimum.

Validates that a Date property is on or after the given minimum.

Validates that a string or array property is at least the given length.

Regex match against a string value. Accepts either a RegExp or a pattern string; strings are promoted to new RegExp(pattern, modifiers).