A simple rate limiter that waits for N milliseconds before running the next callback.

limiter.ts

/*
  How to use:

    import limiter from './limiter'
    const limit = limiter(<wait_time_in_ms>)
    limit(() => console.log('foo'))
    limit(async () => console.log('bar'))
*/
export default (interval : number) => {
  if (interval <= 0) {
    throw new Error("'interval' must be a positive integer")
  }

  const queue : Array<() => (void | Promise<void>)> = []

  const unqueue = () => {
    const callback = queue.shift()
    if (callback) {
      callback()
    }
  }

  setInterval(unqueue, interval)

  return (callback : () => (void | Promise<void>)) => {
    queue.push(callback)
  }
}