Default Values

Every schema builder supports .default(value). When the input is undefined, the default value is used instead — and the result is still validated against the schema's constraints.

import { string, number, array, date, object, type InferType } from '@cleverbrush/schema';

// Static default
const Name = string().default('Anonymous');
Name.validate(undefined); // { valid: true, object: 'Anonymous' }
Name.validate('Alice');   // { valid: true, object: 'Alice' }

// Factory function — useful for mutable defaults like arrays or dates
const Tags = array(string()).default(() => []);

// Works with .optional() — .default() removes undefined from the inferred type
const Port = number().optional().default(3000);
type Port = InferType<typeof Port>; // number

Use a factory function for mutable values (arrays, objects, dates) to avoid shared references:

const Config = object({
  host: string().default('localhost'),
  port: number().default(8080),
  tags: array(string()).default(() => []),
  createdAt: date().default(() => new Date())
});

type Config = InferType<typeof Config>;
// { host: string; port: number; tags: string[]; createdAt: Date }
// All fields are non-optional — defaults fill in missing values

Default values are exposed via .introspect(), making them available for form generation, serialization, and other tooling:

const schema = string().default('hello');
const info = schema.introspect();
console.log(info.hasDefault);    // true
console.log(info.defaultValue);  // 'hello'