polling.ts

polling.ts

export default (fn, ms = 1000) => {
  const connections = new Map();
  let id: number | undefined;
  const poll = async () => {
    if (connections.size > 0)
      await fn().then((results) =>
        connections.forEach((conn) => conn(results))
      );
    if (connections.size > 0) id = setTimeout(poll, ms);
  };
  const setItem = async (cId, fn) => {
    connections.set(cId, fn);
    if (!id) await poll();
  };
  const deleteItem = (cId) => {
    connections.delete(cId);
    if (connections.size === 0) {
      clearTimeout(id);
      id = undefined;
    }
  };
  return { setItem, deleteItem };
};