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這篇文章將為大家詳細(xì)講解有關(guān)React碰到v-if的示例分析,小編覺(jué)得挺實(shí)用的,因此分享給大家做個(gè)參考,希望大家閱讀完這篇文章后可以有所收獲。
代碼:
import React from 'react' const App = () => { const record = { toKe: true, // 貝殼首頁(yè) toSecondHand: true, // 二手房 toFang: true, // 新房 } return ( <div style={{width: 600, margin: '50px auto'}}> <ul> <li> <h4>react常規(guī)寫法</h4> { record.toKe ? <a style={{padding: 20}} href="https://bj.ke.com" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >貝殼首頁(yè)</a> : null } { record.toSecondHand ? <a style={{padding: 20}} href="https://bj.ke.com/ershoufang/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >二手房</a> : null } { record.toFang ? <a style={{padding: 20}} href="https://bj.fang.ke.com/loupan/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >新房</a> : null } </li> </ul> </div> ) } export default App
如上述代碼,我們?cè)陧?xiàng)目中會(huì)遇到很多這樣的寫法, 細(xì)看一下沒(méi)什么問(wèn)題,可是當(dāng)在重構(gòu)老項(xiàng)目的時(shí)候,你會(huì)發(fā)現(xiàn)這個(gè)代碼結(jié)構(gòu)是多么痛苦,特別是如下的結(jié)構(gòu)。
{ record.toFang && record.toKe && record.toSecondHand && <div> <a style={{padding: 20}} href="https://bj.ke.com" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >貝殼首頁(yè)</a> <a style={{padding: 20}} href="https://bj.ke.com/ershoufang/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >二手房</a> <a style={{padding: 20}} href="https://bj.fang.ke.com/loupan/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >新房</a> </div> }
雖然代碼邏輯沒(méi)問(wèn)題,但人生就是這樣,有時(shí)候出場(chǎng)順序真的很重要。突然就想起vue的v-if了。
沒(méi)錯(cuò),回歸主題,就是:react中模擬vue的v-if
先上代碼
import React from 'react' import Hidden from './Hidden' const App = () => { const record = { toKe: true, // 貝殼首頁(yè) toSecondHand: true, // 二手房 toFang: true, // 新房 } return ( <div style={{width: 600, margin: '50px auto'}}> <ul> <li> <h4>react模擬實(shí)現(xiàn)vue中v-if指令</h4> <Hidden visible={record.toKe} tag='span'> <a href="https://bj.ke.com" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >貝殼首頁(yè)</a> </Hidden> <Hidden visible={record.toSecondHand} tag='span' style={{padding: 20}}> <a href="https://bj.ke.com/ershoufang/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >二手房</a> </Hidden> <Hidden visible={record.toFang} tag='p'> <a href="https://bj.fang.ke.com/loupan/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >新房</a> </Hidden> </li> </ul> </div> ) } export default App
簡(jiǎn)單就是封裝Hidden組件,通過(guò)visible去控制是否渲染。
相信聰明的你一定知道怎么去封裝Hidden
筆者剛開(kāi)始是這么寫的
import React, { Component } from 'react' export default class Hidden extends Component { render() { const { visible, children } = this.props const content = visible ? children : null return ( <div> { content } </div> ) } }
如此簡(jiǎn)單,但筆者審查元素的時(shí)候發(fā)現(xiàn),每個(gè)Hidden下的children莫名被嵌套了一層div
如下
原來(lái)的橫著排列的元素,一下子豎著排列了。這可不太好,本來(lái)給我套個(gè)div,我都可以勉強(qiáng)接收,現(xiàn)在連我布局都給我變了。
怎么辦?筆者突然想到使用vue-router中的router-link時(shí),標(biāo)簽是可以通過(guò)tag去替換默認(rèn)標(biāo)簽的。
那我們?cè)俳o它個(gè)tag唄,連帶自定義屬性。
import React, { Component } from 'react' export default class Hidden extends Component { render() { const { visible, children, tag = 'div', ...rest } = this.props const content = visible ? children : null return ( React.createElement(tag, rest, content) ) // return ( // 嘗試用這種方法去實(shí)現(xiàn),發(fā)現(xiàn)不符合react的規(guī)則,所以使用最原始的渲染方法 // React.createElement // `<`${tag}`>` + { content } + `</`${tag}`>` // ) } }
問(wèn)題:筆者的初衷是模擬vue的v-if, 所以對(duì)傳入的children并沒(méi)做太多處理,不建議做多做封裝。有興趣的同學(xué)可以自己玩。
{ record.toFang && record.toKe && record.toSecondHand && <span> <a style={{padding: 20}} href="https://bj.ke.com" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >貝殼首頁(yè)</a> <a style={{padding: 20}} href="https://bj.ke.com/ershoufang/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >二手房</a> <a style={{padding: 20}} href="https://bj.fang.ke.com/loupan/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >新房</a> </span> } <Hidden visible={record.toFang && record.toKe && record.toSecondHand} tag='span'> a href="https://bj.ke.com" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >貝殼首頁(yè)</a> <a style={{padding: 20}} href="https://bj.ke.com/ershoufang/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >二手房</a> <a style={{padding: 20}} href="https://bj.fang.ke.com/loupan/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >新房</a> </Hidden>
其實(shí)感覺(jué)也沒(méi)多大用處hhhh
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