Async polling generator for streams

poll-async-value.js

// Wait utility
const wait = (timeInMs) => {
  return new Promise((resolve) => {
    setTimeout(resolve, timeInMs);
  });
};

let i = 0;

// Fake real time data stream
const fakeLeaderboardData = [
  ['Per', 'Johan', 'Gunnar'],
  ['Anders', 'Sven', 'Ture'],
  ['Lars', 'Olof'],
  ['Göran', 'Agneta', 'Sigurd'],
  ['Lena'],
];

// Fake fetch of real time data
async function fakeFetch(url) {
  if (i === fakeLeaderboardData.length) i = 0;
  const currentLeaderBoard = fakeLeaderboardData[i++];
  return currentLeaderBoard;
}

// Async poller generator that waits for a max amount of ms
// and yields an iterated value for every interval, in ms
async function* getPoller({ url, max, interval }) {
  for (let time = 0; time <= max; time += interval) {
    const leaders = await fakeFetch(url);
    yield* leaders;
    await wait(interval);
  }
}

let pos = 1;

const poller = getPoller({
  url: 'https://fake-api.com/leaderboard',
  max: 1000,
  interval: 500,
});

for await (const value of poller) {
  console.log(`Position: ${pos++}. Name: ${value}`);
}