typedContainer.ts

// Inspired by https://medium.com/@magnusjt/ioc-container-in-nodejs-e7aea8a89600

class UserModel {
  isUser(): boolean {
    return true
  }
}

class UserService {
 constructor(private model: UserModel) {}

 doSomething(): void {}
}

class ContainerError extends Error {
  name = 'ContainerError'
}

class Container<R extends Record<string, unknown> = {}> {
  // @ts-expect-error
  private factories: { [K in keyof R]: (instance: Container<R>) => R[K] } = {}
  // @ts-expect-error
  private resolved: { [K in keyof R]: R[K] } = {}

  set<NewKey extends string, NewValue, NewRegistry extends Omit<R, NewKey> & Record<NewKey, NewValue>>(key: NewKey, factory: (instance: Container<R>) => NewValue): Container<NewRegistry> {
    const newContainer = new Container<NewRegistry>()

    // @ts-expect-error
    newContainer.factories = {
      ...this.factories,
      [key]: factory,
    }

    // @ts-expect-error
    newContainer.resolved = {
      ...this.resolved,
      [key]: undefined,
    }

    return newContainer
  }

  get<K extends keyof R>(key: K): R[K] {
    if (this.resolved[key] === undefined) {
      const resolved = this.factories[key](this)

      if (resolved === undefined || resolved === null) {
        throw new ContainerError(`Error building ${key}: received ${resolved}`)
      }

      this.resolved[key] = resolved
    }

    return this.resolved[key]
  }
}

const container = new Container()
  .set('SomeConstant', () => 4)
  .set('SomeConstant', () => 'constant')
  .set('UserModel', () => new UserModel())
  .set('UserService', (instance) => new UserService(instance.get('UserModel')))

const model = container.get('UserModel');
const service = container.get('UserService');
const constant = container.get('SomeConstant');

console.log(model, service, constant)