PromiseLock or Mutex ?

mutex.js

/**
 * A PromiseLock like object.
 *
 * Used to ensure that we only do one thing at a time on a shared resource.
 *
 * For example, with async iterator:
 *
 * this.readLock = new Mutex()
 * this.readLock.do(async () => {
 *    const data = await itr.next();
 *    // do stuff with itr result
 * })
 *
 * Allows for handling resources that are not concurrency friendly in order.
 */
class Mutex {
  constructor () { this.pendingOperation = null }
  async do (operation) {
    if (this.pendingOperation) await this.pendingOperation
    if (this.pendingOperation) return this.do(operation)

    const promise = operation()
    this.pendingOperation = promise
    const result = await promise
    this.pendingOperation = null
    return result
  }
}