funky

import { Option, some, none } from "https://deno.land/x/funky/mod.ts";
import { isUndefined } from "https://deno.land/x/funky/mod.ts";

const getEnvVar = (key: string): Option<string> => {
  const value = Deno.env.get(key);
  return isUndefined(value) ? none() : some(value);
};

const getHome = getEnvVar("HOME");
const home = getHome.match({
  some: (value: string) => value,
  none: () => "Could not retrieve HOME path from env."
});
console.log(home); // "/home/alice"

const getMadeUpVar = getEnvVar("MADE_UP_VAR");
const madeUpVar = getMadeUpVar.match({
  some: (value: string) => value,
  none: () => "Could not retrieve MADE_UP_VAR"
});
console.log(madeUpVar); // "Could not retrieve MADE_UP_VAR"

import { Result, ok, err } from "https://deno.land/x/funky/mod.ts";

const fetchUser = async (id: number): Promise<Result<User, string>> => {
  const url = `api.com/users/${id}`;
  const response = await fetch(url);

  if (response.status === 404) {
    return err(`User with id ${id} does not exist.`);
  }

  try {
    const user = await response.json();
    return Ok(user as User);
  } catch (error) {
    return err("Parsing the response failed.");
  }
};

console.log(await fetchUser(42)); // ResultOk(user: { id: 42 })
console.log(await fetchUser(-1)); // ResultErr("User with id -1 does not exist.")