用于限流

throttle.ts

export function throttle<R>(func: () => Promise<R>): () => Promise<R> {
  let promise: Promise<R> | null = null
  return () => {
    if (promise) {
      return promise
    } else {
      promise = func()
      promise.finally(() => promise = null)
      return promise
    }
  }
}

throttle2.ts

export function throttle<Args extends any[], R>(func: (...args: Args) => Promise<R>): (...args: Args) => Promise<R> {

  function hash(str: string): number {
    let nr = 1
    let nr2 = 4
    for (let i = 0; i < str.length; i++) {
      nr ^= (((nr & 63) + nr2) * (str.charCodeAt(i))) + (nr << 8)
      nr2 += 3
    }
    return nr
  }

  function hashArgs(args: Args): number {
    return hash(JSON.stringify(args))
  }

  const promises: { [key: number]: Promise<R> } = {}

  return (...args: Args) => {
    const key = hashArgs(args)
    if (promises[key]) {
      return promises[key]
    } else {
      const promise = func(...args)
      promises[key] = promise
      promise.finally(() => delete promises[key])
      return promise
    }
  }
}