12-JSX得class得设置.html

<body>
  <div id='root'>div>
  <script src="./react.js">script>
  <script src="./react-dom.js">script>
  <script src="./babel.min.js">script>
  <script type="text/babel">
    var arr=['111','222','333']

    //只给第一项加active  如果多项要active 可以用插件,后面讲
    ReactDOM.render((
      <ul>
        {arr.map((val,index)=>{
          return (<li key={index} className={index==0?'active':''}>{index}---{val}</li>)
        })
      }
      </ul>
    ),document.getElementById('root'))

  script>
  

 

13-JSX得样式.html

<div id="root">div>
  <script src="./react.js">script>
  <script src="./react-dom.js">script>
  <script src="./babel.min.js">script>
  <script type="text/babel">
  //jsx中元素得style属性不能设置为字符串,应该设置为对象
    // const el=(
);
//样式属性名做key(如果属性名有多个单词,要以驼峰命名, 例如padding-left写成paddingLeft),属性值为value const el=(<div style={{width:'100px',height:'100px',background:'red',paddingLeft:'50px'}}></div>); ReactDOM.render(el,document.getElementById('root')) script>

14-JSX.html

<div id="root">div>
    <script src="./react.js">script>
    <script src="./react-dom.js">script>
    <script src="./babel.min.js">script>
    <script type="text/babel">
      let value="112"
      function change(){
        value *= Math.random()*0.2
        alert(value)//value变了  但视图没有因为value变化而更新
        const el=(<div><p>{value}</p>

15-举例.html

<div id='root'>div>
<script src="./react.js">script>
<script src="./react-dom.js">script>
<script src="./babel.min.js">script>

<script type="text/babel">

 var arr=['aaa','bbb','ccc']

 function render(){
    ReactDOM.render((
      <div>{arr.map((item,index)=>{
      return (
        <div key={index}>
          {item}
          <button onClick={()=>moveUp(index)}>上移</button>
          <button onClick={()=>moveDown(index)}>下移</button>
        </div>
      )

    })}
    </div>),document.getElementById('root'))


 }

function moveDown(index){
  if(index===arr.length-1){
    alert('无法下移')
    return
  }
  let newArr=[]
  newArr=arr.splice(index,1)
  arr.splice(index+1,0,newArr[0])
  render()
}

function moveUp(index){
  if(index===0){
    alert('无法上移')
    return
  }
  let newArr=[]
  newArr=arr.splice(index,1)
  arr.splice(index-1,0,newArr[0])
  render()
}

render()

script>

16-JSX.html

<div id='root'>div>
<script src="./react.js">script>
<script src="./react-dom.js">script>
<script src="./babel.min.js">script>

<script type="text/babel">

 var arr=['aaa','bbb','ccc']

 function render(){
    ReactDOM.render((
      <div>{arr.map((item,index)=>{
      return (
        <div key={index}>
          {item}
          <button onClick={()=>moveUp(index)}>上移</button>
          <button onClick={()=>moveDown(index)}>下移</button>
        </div>
      )

    })}
    </div>),document.getElementById('root'))


 }

function moveDown(index){
  if(index===arr.length-1){
    alert('无法下移')
    return
  }
  let newArr=[]
  newArr=arr.splice(index,1)
  arr.splice(index+1,0,newArr[0])
  render()
}

function moveUp(index){
  if(index===0){
    alert('无法上移')
    return
  }
  let newArr=[]
  newArr=arr.splice(index,1)
  arr.splice(index-1,0,newArr[0])
  render()
}

render()

 

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