element-plus/packages/hooks/use-throttle-render/index.ts

import { onMounted, ref, watch } from 'vue'

import type { Ref } from 'vue'
import type { TimeoutHandle } from '@element-plus/utils/types'

export default function (loading: Ref<boolean>, throttle = 0) {
  if (throttle === 0) return loading
  const throttled = ref(false)
  let timeoutHandle: TimeoutHandle = 0

  const dispatchThrottling = () => {
    if (timeoutHandle) {
      clearTimeout(timeoutHandle)
    }
    timeoutHandle = window.setTimeout(() => {
      throttled.value = loading.value
    }, throttle)
  }
  onMounted(dispatchThrottling)

  watch(
    () => loading.value,
    (val) => {
      if (val) {
        dispatchThrottling()
      } else {
        throttled.value = val
      }
    }
  )
  return throttled
}