Limit concurrent jQuery ajax requests to at most 6 at a time, and queue the rest.

ajaxPool.js

const ajaxPool = {
  queue: [],
  reqCount: 0,
  activeCount: 0,
  maxCount: parseInt(searchParams.get('ajaxLimit')) || 6,
  add(obj) {
    this.reqCount++
    const originalSuccess = obj.success
    const originalError = obj.error
    const callback = () => {
      this.reqCount--
      if (this.activeCount <= this.maxCount && this.queue.length > 0) {
        $.ajax(this.queue.shift())
      } else {
        this.activeCount--
      }
    }
    obj.success = (resp, xhr, status) => {
      callback()
      if (originalSuccess) {
        originalSuccess(resp, xhr, status)
      }
    }
    obj.error = (xhr, status, error) => {
      callback()
      if (originalError) {
        originalError(xhr, status, error)
      }
    }

    if (this.activeCount < this.maxCount) {
      this.activeCount++
      $.ajax(obj)
    } else {
      this.queue.push(obj)
    }
  }
}