optional

Creates an optional schema.

const Schema = v.optional<TWrapped, TDefault>(wrapped, default_);

Generics

• TWrapped extends BaseSchema<unknown, unknown, BaseIssue<unknown>>
• TDefault extends Default<TWrapped, undefined>

Parameters

• wrapped TWrapped
• default_ TDefault

Explanation

With optional the validation of your schema will pass undefined inputs, and if you specify a default_ input value, the schema will use it if the input is undefined. For this reason, the output type may differ from the input type of the schema.

Important: When used in object schemas, if a key is missing and no default_ value is provided, the schema's pipe (including transformations) will not be executed. To ensure pipes run for missing keys, provide a default_ value.

Note that optional does not accept null as an input. If you want to accept null inputs, use nullable, and if you want to accept null and undefined inputs, use nullish instead. Also, if you want to set a default output value for any invalid input, you should use fallback instead.

Returns

• Schema OptionalSchema<TWrapped, TDefault>

Examples

The following examples show how optional can be used.

Optional string schema

Schema that accepts string and undefined.

const OptionalStringSchema = v.optional(v.string(), "I'm the default!");

Optional date schema

Schema that accepts Date and undefined.

By using a function as the default_ parameter, the schema will return a new Date instance each time the input is undefined.

const OptionalDateSchema = v.optional(v.date(), () => new Date());

Optional entry schema

Object schema with an optional entry.

const OptionalEntrySchema = v.object({
  key: v.optional(v.string()),
});

Default to undefined

By default, when an object input is missing an optional entry, the corresponding key is omitted from the output. To always include the key in the output with an undefined value, pass a function that returns undefined as the default_ parameter.

const OptionalEntrySchema = v.object({
  key: v.optional(v.string(), () => undefined),
});

Unwrap optional schema

Use unwrap to undo the effect of optional.

const OptionalNumberSchema = v.optional(v.number());
const NumberSchema = v.unwrap(OptionalNumberSchema);

Optional with pipes

When using optional in a pipe, the pipe actions only execute if a default_ value is provided or the key is present. This applies to all pipe actions including transform, check, and others.

const SchemaWithoutDefault = v.object({
  isActive: v.pipe(
    v.optional(v.string()),
    v.transform((value) => value === 'true') // Does not run for missing keys
  ),
}); // Output type: { isActive?: boolean }

const SchemaWithDefault = v.object({
  isActive: v.pipe(
    v.optional(v.string(), 'false'), // Default value provided
    v.transform((value) => value === 'true') // Runs for missing keys too
  ),
}); // Output type: { isActive: boolean }

Related

The following APIs can be combined with optional.

Schemas

any, array, bigint, blob, boolean, custom, date, enum, exactOptional, file, function, instance, intersect, lazy, literal, looseObject, looseTuple, map, nan, never, nonNullable, nonNullish, nonOptional, null, nullable, nullish, number, object, objectWithRest, picklist, promise, record, set, strictObject, strictTuple, string, symbol, tuple, tupleWithRest, undefined, undefinedable, union, unknown, variant, void

Methods

assert, config, fallback, getDefault, getDefaults, getFallback, getFallbacks, is, message, parse, parser, pipe, safeParse, safeParser, unwrap

Actions

check, brand, description, flavor, guard, metadata, partialCheck, rawCheck, rawTransform, readonly, title, transform

Utils

entriesFromList, isOfKind, isOfType