Model on FE

model.ts

import { Profile } from "./profile";
import { User } from "./user";

const types = {
  user: User,
  profile: Profile,
};

export class Model {
  static fromJson<
    Value extends InstanceType<typeof types[T]>,
    T extends keyof typeof types
  >(json: { type: T; [key: string]: any }): Value;

  static fromJson<
    Value extends InstanceType<typeof types[T]>,
    T extends keyof typeof types
  >(json: { type: T; [key: string]: any }[]): Value[];

  static fromJson(json: any): any {
    if (Array.isArray(json)) {
      return Model.fromJsonArray(json);
    }

    return Model.fromJsonSingle(json);
  }

  private static fromJsonArray<
    Value extends InstanceType<typeof types[T]>,
    T extends keyof typeof types
  >(json: Array<{ [key: string]: any; type: T }>): Value[] {
    return json.map((item) => Model.fromJsonSingle(item));
  }

  private static fromJsonSingle<
    Value extends InstanceType<typeof types[T]>,
    T extends keyof typeof types
  >(json: { [key: string]: any; type: T }): Value {
    const type = json["type"] as keyof typeof types;

    if (!type) {
      throw new Error("Type is missing from JSON");
    }

    if (!types[type]) {
      throw new Error(`Type ${type} is not supported`);
    }

    const model = new types[type]();

    for (const key in json) {
      // Infer key type from model
      if (typeof json[key] === "object" && json[key].hasOwnProperty("type")) {
        // @ts-ignore
        model[key] = Model.fromJson(json[key]);

        continue;
      }

      if (
        Array.isArray(json[key]) &&
        json[key].length > 0 &&
        json[key][0].hasOwnProperty("type")
      ) {
        // @ts-ignore
        model[key] = json[key].map((item: any) => Model.fromJson(item));
        continue;
      }

      // @ts-ignore
      model[key] = json[key];
    }

    return model as Value;
  }
}

profile.ts

export class Profile {
  id: number;
  avatar: string;

  constructor() {
    this.id = 0;
    this.avatar = "";
  }
}

test.ts

import { Model } from "./model";

const users = Model.fromJson([
  {
    id: 1,
    name: "John Doe",
    type: "user",
  },
  {
    id: 2,
    name: "Jane Doe",
    type: "user",
  },
]);

const user = Model.fromJson({
  id: 1,
  name: "John Doe",
  type: "user",
});

console.log(user.profile?.id);
console.log(users[0].profile?.id);

user.ts

import { Profile } from "./profile";

export class User {
  id: number;
  name: string;
  email: string;
  phone: string;
  address: string;
  city: string;
  state: string;
  zip: string;
  country: string;
  image: string;
  profile?: Profile;

  constructor() {
    this.id = 0;
    this.name = "";
    this.email = "";
    this.phone = "";
    this.address = "";
    this.city = "";
    this.state = "";
    this.zip = "";
    this.country = "";
    this.image = "";
  }
}