RunTypes

Supported Types

Comprehensive list of supported TypeScript types and feature comparison with other validation libraries.

@mionjs/run-types supports a comprehensive set of TypeScript types.
The long term goal is to fully support all typescript features for full compatibility.

Type Support Comparison

Type Category	Type	run-types	Zod	Typia	AJV	TypeBox
Primitives	`string`	✅	✅	✅	✅	✅
	`number`	✅	✅	✅	✅	✅
	`boolean`	✅	✅	✅	✅	✅
	`bigint`	✅	✅	✅	❌	✅
	`symbol`	✅	✅	✅	❌	✅
	`null`	✅	✅	✅	✅	✅
	`undefined`	✅	✅	✅	❌	✅
	`void`	✅	✅	✅	❌	✅
	`never`	✅	✅	✅	❌	✅
	`any`	✅	✅	✅	✅	✅
	`unknown`	✅	✅	✅	✅	✅
Literals	String literals	✅	✅	✅	✅	✅
	Number literals	✅	✅	✅	✅	✅
	Boolean literals	✅	✅	✅	✅	✅
	Template literals	✅	❌	✅	❌	✅
Objects	`interface`	✅	✅	✅	✅	✅
	`type` aliases	✅	✅	✅	✅	✅
	`class`	✅	❌	✅	❌	❌
	Nested objects	✅	✅	✅	✅	✅
	Optional properties	✅	✅	✅	✅	✅
	Readonly properties	✅	✅	✅	❌	✅
	Index signatures	✅	✅	✅	✅	✅
Collections	`Array<T>`	✅	✅	✅	✅	✅
	`Tuple`	✅	✅	✅	✅	✅
	`Record<K, V>`	✅	✅	✅	✅	✅
Native Objects	`Date`	✅	✅	✅	❌	✅
	`RegExp`	✅	❌	✅	❌	❌
	`Map<K, V>`	✅	✅	✅	❌	❌
	`Set<T>`	✅	✅	✅	❌	❌
Enums	Numeric enums	✅	✅	✅	❌	❌
	String enums	✅	✅	✅	❌	❌
	Const enums	✅	❌	✅	❌	❌
Unions & Intersections	Union types	✅	✅	✅	✅	✅
	Discriminated unions	🚀	✅	✅	✅	✅
	Intersection types	✅	✅	✅	✅	✅
Utility Types	`Partial<T>`	✅	✅	✅	❌	✅
	`Required<T>`	✅	✅	✅	❌	✅
	`Pick<T, K>`	✅	✅	✅	❌	✅
	`Omit<T, K>`	✅	✅	✅	❌	✅
	`Exclude<T, U>`	✅	❌	✅	❌	✅
	`Extract<T, U>`	✅	❌	✅	❌	✅
	`NonNullable<T>`	✅	✅	✅	❌	❌
	`Awaited<T>`	✅	❌	✅	❌	✅
	`Parameters<F>`	✅	❌	✅	❌	✅
	`ReturnType<F>`	✅	❌	✅	❌	✅
String Utilities	`Uppercase<S>`	⚠️	❌	✅	❌	✅
	`Lowercase<S>`	⚠️	❌	✅	❌	✅
	`Capitalize<S>`	⚠️	❌	✅	❌	✅
	`Uncapitalize<S>`	❌	❌	✅	❌	✅
Functions	Function types	💎	✅	✅	❌	✅
	Method signatures	✅	❌	✅	❌	❌
	Call signatures	✅	❌	✅	❌	❌
	Rest parameters	✅	✅	✅	❌	✅
Advanced	Circular references	✅	❌	✅	❌	⚠️
	Generic types	✅	✅	✅	❌	✅
	Conditional types	⚠️	❌	✅	❌	⚠️
	Mapped types	❌	❌	✅	❌	❌
	Type inference	❌	❌	x	❌	❌

⚠️ = Partial support with limitations

🚀 = mion has optimized type checking for discriminated unions.

💎 = mion is the only framework from the table that can extract types directly from functions

import {reflectFunction} from '@mionjs/run-types';

function sayHello(name: string): string {
    return `Hello ${name}`;
}

const fnType = reflectFunction(sayHello);
// fnType = FunctionRunType<type (name: string) => string>

Feature Comparison

Feature	run-types	Zod	Typia	AJV	TypeBox
Core
Type inference from TS	✅	❌	✅	❌	❌
Schema-first approach	❌	✅	❌	✅	✅
JIT compilation	✅	❌	AOT	✅	✅
TSC build required	✅	❌	✅	❌	❌
Validation
Type validation	✅	✅	✅	✅	✅
Strict validation	✅	✅	✅	✅	✅
Error messages	✅	✅	✅	✅	✅
Custom error messages	✅	✅	✅	✅	✅
Serialization
JSON serialization	✅	❌	✅	❌	❌
Binary serialization	✅	❌	PROTOBUF	❌	❌
Date handling	✅	❌	✅	❌	✅
BigInt handling	✅	❌	✅	❌	✅
Map/Set handling	✅	❌	✅	❌	❌
Other
Mock data generation	✅	❌	✅	❌	❌
Function reflection	✅	❌	❌	❌	❌
AOT code generation	✅	❌	✅	❌	✅

Approach Comparison

Schema-First (Zod, AJV)

With schema-first libraries, you define schemas separately from your TypeScript types:

import {z} from 'zod';

// Zod example - schema is source of truth
const UserSchema = z.object({
    name: z.string(),
    age: z.number(),
    email: z.string().email(),
});
type User = z.infer<typeof UserSchema>;

Pros: No build step, works everywhere Cons: Duplicate definitions, schemas can drift from actual types

Type-First (run-types, Typia)

With type-first libraries, TypeScript types are the source of truth:

import {createIsTypeFn} from '@mionjs/run-types';
import {FormatEmail} from '@mionjs/type-formats/StringFormats';

// run-types example - TypeScript is source of truth
interface User {
    name: string;
    age: number;
    email: FormatEmail; // Using type formats for validation
}

const validate = await createIsTypeFn<User>();

Pros: Single source of truth, no schema duplication Cons: Requires TypeScript compiler integration

run-types vs Typia: Function Reflection

The key difference between run-types and Typia is function reflection. While both are type-first, Typia cannot extract types directly from function signatures, requiring you to declare types separately and pass them as generic parameters.

Typia + Hono example: (required to create validators manually)

import {Hono} from 'hono';
import {typiaValidator} from '@hono/typia-validator';
import typia from 'typia';

interface IBbsArticle {
    // ❌ Must declare type separately
    id: string;
    title: string;
    body: string;
    created_at: string;
}

// ❌ Must create validator with explicit generic type
const validate = typia.createValidate<IBbsArticle>();

const app = new Hono();

app.post(
    '/',
    typiaValidator('json', validate), // ❌ Pass validator as middleware
    (c) => {
        const data = c.req.valid('json');
        return c.json({id: data.id, title: data.title, body: data.body});
    }
);

mion example (types extracted from functions and validated automatically):

import {Routes, route} from '@mionjs/router';

interface Article {
    id: string;
    title: string;
    body: string;
}

type NewArticle = Omit<Article, 'id'>;

declare function generateId(): string;

// ✅ Types are extracted directly from the function signature
const routes = {
    createArticle: route((ctx, article: NewArticle): Article => {
        return {id: generateId(), ...article};
    }),
} satisfies Routes;

With mion, the router automatically extracts parameter and return types from your route handlers — no separate type declarations, no generic parameters, no middleware wiring, and no risk of types drifting out of sync.

When to Use run-types

✅ Use run-types when:

You want TypeScript types as the single source of truth
You need JSON serialization with complex types (Date, Map, Set, BigInt)
You need binary serialization for performance
You want mock data generation from types
You're building APIs with mion

❌ Consider alternatives when:

You need to share schemas with non-TypeScript consumers
You're building a library consumed by vanilla JavaScript
You need schemas defined at runtime

at runtime

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RunTypes Overview

JIT compilation library that generates optimized validation, serialization, and mocking functions from TypeScript types.

Type Formats

Validation and transformation formats for strings and numbers using TypeScript types.