如何使用反应挂钩有条件地重置 state 计数

Question

用户提交我的表单后， handleSubmit function 运行并计算li元素的数量，其中 class 名称在我的div中包含“show”，显示所有搜索结果。 它将这些计数与setStoreCount(prevCount => prevCount + 1) ，我更新了我的FAQ {searchCount} UI，显示搜索结果的数量

useEffect(() => {
  setSearchCount(storeCount) // collect all storeCount
}, [storeCount])

问题：假设第一次搜索得到 5 个结果。

然后 UI 将显示FAQ 5 。 如果您再次搜索相同的内容，您仍然会得到 5 个结果，并且希望 UI 仍会显示FAQ 5 ，但由于storeCount无法重置为0 ，它会显示FAQ 10 (5 + 5)，然后显示FAQ 15 (5 + 5 + 5 ） 等等。

因为只要storeCount更改，我的 useEffect 就会有条件地运行，因此我无法将其重置为 0，因为那样我将始终显示FAQ 0 。

如何在下面的代码中刷新每次搜索的计数时显示搜索结果的数量？

import React, { useState, useRef, useEffect } from 'react'

import ContentsWrap from '../../components/contents-wrap'
import FrequentList from './tabs/frequent'
import EstimateList from './tabs/estimate'
import ReturnList from './tabs/return'
import EtcList from './tabs/etc'
import SubsidiaryList from './tabs/subsidiary'
import ServiceList from './tabs/service'
import InList from './tabs/in'
import OutList from './tabs/out'

import styles from './index.module.scss'

export default function FAQ () {
  const [tab, setTab] = useState('frequent')
  const [storeText, setStoreText] = useState('') // stores searchbar text as user types
  const [searchText, setSearchText] = useState('') // sends searchbar text to List component props on form submit
  const [storeCount, setStoreCount] = useState(0) // stores count of each li element className that includes 'show'
  const [searchCount, setSearchCount] = useState(0) // shows search count in UI
  const searchContainer = useRef(null)
  const handleSubmit = e => {
    e.preventDefault()
    setSearchText(storeText)
    setTab('all')
    setTimeout(() => {
      // gets all <ul> children of <div class = "faq-list-wrap">
      for (let i = 0; i < searchContainer.current.children.length; i++) {
      // gets all <li> children of each <ul>
        for (let j = 0; j < searchContainer.current.children[i].children.length; j++) {
        // checks if each li class name has 'show'
          if (searchContainer.current.children[i].children[j].className.includes('show')) {
            console.log('count added')
            setStoreCount(prevCount => prevCount + 1)
          }
        }
      }
    }, 100) // setTimeOut needed to target searchContainer after search and not before
  }
  const handleChange = newId => {
    setTab(newId)
    setStoreText('') // clear input value on tab click
    setSearchText('') // show all search items on tab click
  }
  useEffect(() => {
    setSearchCount(storeCount) // collect all storeCount
  }, [storeCount])
  return (
    <ContentsWrap>
      <div className="content-wrap content-width">
        {/* <!-- S: faq-wrap --> */}
        <div className="faq-wrap">
          <div className="faq-title-wrap"><h2 className="title">FAQ {searchCount}</h2></div>
          <form onSubmit={handleSubmit}>
            <input
              type="text"
              placeholder="Search"
              className={styles.searchBox}
              value={storeText}
              onChange={e => {
                setStoreText(e.target.value)
              }}
            />
          </form>

          {/* <!-- S: faq-list-wrap --> */}
          <div className="faq-list-wrap" ref={searchContainer} >
            {tab === 'all' && (
              <>
                <FrequentList searchText={searchText} />
                <EstimateList searchText={searchText} />
                <ReturnList searchText={searchText} />
                <EtcList searchText={searchText} />
                <SubsidiaryList searchText={searchText} />
                <ServiceList searchText={searchText} />
                <InList searchText={searchText} />
                <OutList searchText={searchText} />
              </>
            )}
            {tab === 'frequent' && (
              <FrequentList searchText={searchText}/>
            )}
            {tab === 'estimate' && (
              <EstimateList searchText={searchText}/>
            )}
            {tab === 'return' && (
              <ReturnList searchText={searchText} />
            )}
            {tab === 'subsidiary' && (
              <SubsidiaryList searchText={searchText} />
            )}
            {tab === 'service' && (
              <ServiceList searchText={searchText} />
            )}
            {tab === 'in' && (
              <InList searchText={searchText} />
            )}
            {tab === 'out' && (
              <OutList searchText={searchText} />
            )}
            {tab === 'etc' && (
              <EtcList searchText={searchText} />
            )}
          </div>
          {/* <!-- E: faq-list-wrap --> */}
        </div>
        {/* <!-- E: faq-wrap --> */}
      </div>
    </ContentsWrap>
  )
}

Answer 1

这里的问题在于您的setStoreCount逻辑。

在你的for循环的这一行中：

if (searchContainer.current.children[i].children[j].className.includes('show')) {
    console.log('count added')
    setStoreCount(prevCount => prevCount + 1)
}

如果prevCount为 5，它将向prevCount添加 1（这是第一次搜索的结果数，它添加 1 等等。

您可以做的是在添加找到的元素数量之前重置storeCount 。 像这样：

setTimeout(() => {
      setStoreCount(0)
      // gets all <ul> children of <div class = "faq-list-wrap">
      for (let i = 0; i < searchContainer.current.children.length; i++) {
      // gets all <li> children of each <ul>
        for (let j = 0; j < searchContainer.current.children[i].children.length; j++) {
        // checks if each li class name has 'show'
          if (searchContainer.current.children[i].children[j].className.includes('show')) {
            console.log('count added')
            setStoreCount(prevCount => prevCount + 1)
          }
        }
      }
    }, 100) // setTimeOut needed to target searchContainer after search and not before

但这可能会像，它显示FAQ 0 ，然后是循环后计数的rest。 所以我建议在设置计数之前先计算它，就像这样。

setTimeout(() => {
      let count = 0
      // gets all <ul> children of <div class = "faq-list-wrap">
      for (let i = 0; i < searchContainer.current.children.length; i++) {
      // gets all <li> children of each <ul>
        for (let j = 0; j < searchContainer.current.children[i].children.length; j++) {
        // checks if each li class name has 'show'
          if (searchContainer.current.children[i].children[j].className.includes('show')) {
            console.log('count added')
            count++
          }
        }
      }
      setStoreCount(count)
    }, 100) // setTimeOut needed to target searchContainer after search and not before

Answer 2

您的循环只是永久增加 storeCount 。 您应该在循环开始时从零开始一个计数器，然后使用 setStoreCount 将计数器的最终值分配给您的 storeCount。