Deepkit Runtime Types

External Types

External Classes

Since TypeScript does not include type information per default, imported types/classes from other packages (that did not use @deepkit/type-compiler) will not have type information available.

To annotate types for an external class, use annotateClass and make sure this function is executed in the bootstrap phase of your application before the imported class is used somewhere else.

import { MyExternalClass } from 'external-package';
import { annotateClass } from '@deepkit/type';

interface AnnotatedClass {
    id: number;
    title: string;


//all uses of MyExternalClass return now the type of AnnotatedClass

//MyExternalClass can now also be used in other types
interface User {
    id: number;
    clazz: MyExternalClass;

MyExternalClass can now be used in serialization functions and in the reflection API.

To following shows how to annotate generic classes:

import { MyExternalClass } from 'external-package';
import { annotateClass } from '@deepkit/type';

class AnnotatedClass<T> {
    id!: T;

annotateClass(ExternalClass, AnnotatedClass);

Import Type

The import type syntax is designed by TypeScript to avoid importing actual JavaScript code and use it only for type-checking. This is useful for example when you want to use a type from a package that is not available at runtime, but only at compile-time or if you don't want to actually load that package at runtime.

Deepkit supports the reasoning of import type and will not generate any runtime code. This means if you use import type, no type information will be available at runtime.