Schemas and strict types

const User = JIT.object({
  id: JIT.number().int32().positive(),
  name: JIT.string().min(3).max(80),
  email: JIT.string().email(),
  role: JIT.union(JIT.literal("admin"), JIT.literal("member")),
});

type User = JIT.Typeof<typeof User>;

The runtime AST has a stable { type, _type, def, annotations } shape. _type is always null at runtime and carries inference only at compile time.

Object transforms

User.partial();
User.partial("email");
User.required();
User.pick("id", "name");
User.omit("email");
User.extend({ active: JIT.boolean() });

Transforms return new schemas and do not mutate the original.

Composition

Use union, xor, intersection, not, when/where, refinements, codecs and template literals as declarative schema nodes. TypeScript rejects invalid literal defaults when their value can be checked statically against string/number constraints.

JIT.string().min(5).default("hello");
// JIT.string().min(5).default("no"); // TypeScript error

Runtime validation remains authoritative for dynamic strings and numbers whose literal value is not known to TypeScript.