nevermind, i actually did it now 4 minutes after complaining because i saw there’s code examples here:

https://github.com/LemmyNet/lemmy/blob/ecc9469a02e63eab4e19093007c7ba6db0dca079/api_tests/src/shared.ts#L4

this works:

import { GetPost, GetPostResponse, LemmyHttp, Login } from "lemmy-js-client";

export interface API {
  client: LemmyHttp;
  auth: string;
}

export let alpha: API = {
  client: new LemmyHttp("https://sh.itjust.works"),
  auth: "",
};

let formAlpha: Login = {
  username_or_email: "username",
  password: "password",
};

export async function getPost(
  api: API,
  post_id: number
): Promise<GetPostResponse> {
  let form: GetPost = {
    id: post_id,
    auth: api.auth,
  };
  return api.client.getPost(form);
}

getPost(alpha, 1).then((res) => {
  console.log(res);
});