Svelte Store with Custom Class in Typescript

account.ts

/*
I recently jumped into svelte programming and wanted to create a class/singleton that could double as a reactive writable store. 
I did things very wrong until people on the discord confirmed how wrong my implementation was so I wanted to provide a simple example.
So below is a simple account store you can use. I'm not sure if it's optimal or even correct, but it's better than my first attempt. 
Feel free to provide feedback.
*/
```

import { writable } from "svelte/store";
// fake stuff for example
import {AuthUser, GuestUser, authService} from "./utils";

export default class Account {
  public subscribe: Function;
  private _set: Function;
  private _update: Function;
  private authUser: AuthUser;
  private isAuthenticated: Boolean;

  constructor() {
    this.authUser = new GuestUser();
    this.isAuthenticated = false;
    let {subscribe, set, update} = writable(this);
    this.subscribe = ubscribe;
    this._set = set;
    this._update = update;
  }

  login(form: AuthForm): Boolean {
    return authService.login(form).then((authUser) => {
      this._update((that) => {
        that.authUser = authUser;
        that.isAuthenticated = true;
        return that;
      });
      return true;
    }).catch((e: InvalidLogin) => {
      this.clearUser();
      return false;
    });
  }
  clearUser(): Boolean {
    this._update((that) => {
        that.authUser = new GuestUser();
        thas.isAuthenticated = false;
    });
    return true;
   }
}

/*
Then in your .svelte, you could import a singleton/instance of the above class and use it as a store:
{#if $account.isAuthenticated }
<p> User: $account.authUser.name </p>
{:else}
<p> Need to login </p
{/if}
*/

Please fix the typo in line 24
subscribe instead of ubscribe.