fake-data.service.js

const data = { userName: "test user" };
const delay = 1200;
const errorChance = 0.2;

export function fetchData() {
  return new Promise((rs, rj) => {
    setTimeout(
      () =>
        Math.random() > errorChance ? rs(data) : rj("Something went wrong"),
      delay
    );
  });
}

fetchData().then(console.log);