Serialize a series of async requests called simultaneously

serialize.ts

const promises: Record<string, Promise<void>> = {};

/**
 * Serializes a series of promise-returning function calls to ensure they
 * occur linearly (as FIFO) rather than concurrently. To group calls that
 * are to be serialized together, send a matching key.
 */
export async function serialize(key: string, callback: () => Promise<void>) {
  if (promises[key]) {
    await promises[key];
  }

  if (!promises[key]) {
    promises[key] = callback();
    await promises[key];
    delete promises[key];
  } else {
    serialize(key, callback);
  }
}