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2018-06-02-react-first-day.html
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2018-06-02-react-first-day.html
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<h1 id="react-学习笔记day-01"><a href="#react-学习笔记day-01" class="headerlink" title="react 学习笔记day-01"></a>react 学习笔记day-01</h1><h2 id="介绍JSX"><a href="#介绍JSX" class="headerlink" title="介绍JSX "></a>介绍JSX </h2><blockquote>
<p><code>const element = <h1>Hello, world!</h1></code> </p>
</blockquote>
<p>它称为JSX，是JavaScript的语法的扩展。 </p>
<h3 id="选择JSX的理由："><a href="#选择JSX的理由：" class="headerlink" title="选择JSX的理由："></a>选择JSX的理由：</h3><p>React拥抱渲染逻辑与其他UI逻辑固有耦合的事实：事件如何处理，状态如何随事件变化以及数据如何准备显示。<br>通过将标记和逻辑放入单独的文件中，React不再人为地分离技术，而是将问题与称为“组件”的松散耦合单元分隔开来。 </p>
<p>在JSX中嵌入表达式 </p>
<p>下面例子中，声明一个变量<code>name</code>,然后在JSX中使用它包装在大括号中： </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">const name = 'Josn Lai';</span><br><span class="line">const elenment = <h1>Hello , {name}</h1>;</span><br><span class="line"></span><br><span class="line">ReactDOM.render(</span><br><span class="line"> element,</span><br><span class="line"> document.getElementById('root')</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<p>可以在JSX的大括号中（<code>{}</code>）放入任何有效的JavaScript表达式。<br>下例中，将调用JavaScript函数的结果嵌入到<code>formatName（user）</code>到<code><h1></code>元素中 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">function formatName(user){</span><br><span class="line"> return user.firstName + ' ' + user.lastName;</span><br><span class="line">}</span><br><span class="line">const user = {</span><br><span class="line"> firstName: 'lai',</span><br><span class="line"> lastName: 'binghong'</span><br><span class="line">};</span><br><span class="line"></span><br><span class="line">const element = (</span><br><span class="line"> <h1></span><br><span class="line"> Hello,{formatName(user)}!</span><br><span class="line"> </h1></span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">ReactDOM.render(</span><br><span class="line"> elememt,</span><br><span class="line"> document.getElementById('root');</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<h3 id="JSX也是一个表达式"><a href="#JSX也是一个表达式" class="headerlink" title="JSX也是一个表达式"></a>JSX也是一个表达式</h3><p>编译之后，JSX表达式变成常规的JavaScript函数调用并评估为JavaScript对象。这意味着可以在if语句和for循环中是用JSX将其分配给变量，将其作为参数接受，并从函数中返回： </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">function getGreeting(user){</span><br><span class="line"> if(user){</span><br><span class="line"> return <h1>Hello，{formatName(user)}!</h1></span><br><span class="line"> }</span><br><span class="line"> return <h1>Hello, Stranger.</h1></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>使用JSX指定属性 </p>
<p>可以使用引号将字符串文字指定为属性 </p>
<blockquote>
<p><code>const element = <div tabIndex = “0”></div></code>; </p>
</blockquote>
<p>也可以使用大括号将javascript表达式嵌入到属性中 </p>
<blockquote>
<p><code>const element = <img src={user.avatarUrl}></img></code>; </p>
</blockquote>
<p>在属性中嵌入javascript表达式时，请勿将大括号括起来，应该使用引号（用于字符串值）或大括号（用于表达式），但是不可以同时使用同一个属性<br><strong>JSX的命名一般用camelCase，驼峰式命名。class => className ,tabindex => tabIndex.</strong></p>
<p>用JSX可以包含子项，单标签用闭合 </p>
<blockquote>
<p><code>const element = <img src = {user.avatarUrl}/>;</code></p>
</blockquote>
<p>JSX标签可能包含子项： </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">const element = (</span><br><span class="line"> <div></span><br><span class="line"> <h1>Hello!</h1></span><br><span class="line"> <h2>xxx</h2></span><br><span class="line"> <div></span><br><span class="line"> ccc</span><br><span class="line"> </div></span><br><span class="line"> </div></span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<h3 id="JSX防止注入攻击"><a href="#JSX防止注入攻击" class="headerlink" title="JSX防止注入攻击"></a>JSX防止注入攻击</h3><p>默认情况下，react DOM 在渲染之前转义嵌入在JSX中的任何值，因此它确保不会注入任何未明确写入应用程序的内容，在呈现前，所有内容都会转换为字符串，有助于防止XSS攻击</p>
<h3 id="JSX表示对象"><a href="#JSX表示对象" class="headerlink" title="JSX表示对象"></a>JSX表示对象</h3><p>Babel将JSX编译为 <code>React.createElement()</code>调用。<br>下方两个例子是相同的：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">const element = (</span><br><span class="line"> <h1 className = "show"></span><br><span class="line"> Hello !</span><br><span class="line"> </h1></span><br><span class="line">);</span><br><span class="line"> </span><br><span class="line">const element = React.createElement(</span><br><span class="line"> 'h1',</span><br><span class="line"> {className: 'show'},</span><br><span class="line"> 'Hello!'</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<p><code>React.createElement()</code>执行一些检查以帮助编写无措代码，但本质上它会创建一个如下对象：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">const element = {</span><br><span class="line"> type: 'h1',</span><br><span class="line"> props: {</span><br><span class="line"> className :'show',</span><br><span class="line"> children: 'Hello!'</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h2 id="渲染元素"><a href="#渲染元素" class="headerlink" title="渲染元素"></a>渲染元素</h2><p>元素时React 应用程序的最小构建块<br>一个元素描述了你想在屏幕上看到的内容<br>与浏览器DOM元素不同，React元素时普通元素，创建起来很便宜，React DOM负责更新DOM以匹配React元素 </p>
<h3 id="将元素渲染到DOM中"><a href="#将元素渲染到DOM中" class="headerlink" title="将元素渲染到DOM中"></a>将元素渲染到DOM中</h3><p>假设div存在于html某个文件中的某个地方</p>
<blockquote>
<p><code><div id="root"></div></code> </p>
</blockquote>
<p>我们称之为“根”DOM节点，因为它内容部的所有内容都将由React DOM管理<br>仅使用React 构建的应用程序通常具有单个根DOM节点，如果将React集成到现有的应用程序中，则可以根据需要拥有尽可能多的独立根DOM节点。<br>要将React元素渲染到根DOM节点中，请将两者传递给<code>ReactDOM.render()</code>; </p>
<blockquote>
<p><code>const element = <h1>Hello,world</h1>;</code><br><code>ReactDOM.render(element,documentById('root'));</code></p>
</blockquote>
<p>更新呈现的元素<br>React元素时不可变的，一旦创建了一个元素，就不能更改其子元素或者属性。<br>更新Ui的唯一方法是创建一个新元素并将其传递给<code>ReactDOM.reader()</code></p>
<p>时钟例子 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">function tick(){</span><br><span class="line"> const element = (</span><br><span class="line"> <div></span><br><span class="line"> <h1>1</h1></span><br><span class="line"> <h1>2</h1></span><br><span class="line"> </div></span><br><span class="line"> );</span><br><span class="line"> ReactDOM.render(element,document.getElementById('root'));</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">setInterval(tick, 1000);</span><br></pre></td></tr></table></figure>
<h3 id="组件和道具-props"><a href="#组件和道具-props" class="headerlink" title="组件和道具(props)"></a>组件和道具(props)</h3><p>组件是讲用户界面独立分开，可重复使用的部分，并且可独立思考每一部分</p>
<h3 id="功能和类组件"><a href="#功能和类组件" class="headerlink" title="功能和类组件"></a>功能和类组件</h3><p>定义组件的最简单方法是编写一个javascript函数 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">function Welcome(x){</span><br><span class="line"> return <h1>你好，{x.name}</h1>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>上面的javascript函数一个有效的React组件，因为它接受一个包含数据的‘x’（代表属性）对象参数并返回一个React元素，我们称这些组件为‘功能性’，因为它们实际上是JavaScript功能 </p>
<p>也可以使用ES6类来定义组件： </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">class Welcome extends React.Compoent{</span><br><span class="line"> render(){</span><br><span class="line"> return <h1>hello, {this.x.name}</h1></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>渲染组件</p>
<p>React元素可以表示DOM标签</p>
<blockquote>
<p><code>const element = <div/>;</code></p>
</blockquote>
<p>也可以表示用户定义的组件</p>
<blockquote>
<p><code>const element =<Welcome name="Lbh">;</code></p>
</blockquote>
<p>当React查看表示用户定义组件的元素时，它会将JSX属性作为单个对象传递给此组件，我们称这个组件为道具 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">function Welcome(props){</span><br><span class="line"> return <h1>hello!{props.name}</h1>;</span><br><span class="line"> }</span><br><span class="line"> const element = <Welcome name="Lbh"/>;</span><br><span class="line"> ReactDOM.render(</span><br><span class="line"> element,</span><br><span class="line"> documemt.getElementById('root')</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<p><strong>注意：始终使用大写字母开始组件名称。</strong></p>
<p>构成组件</p>
<p>组件可以在其输出中引用其他组件，一个按钮、一个窗体、一个对话框、一个屏幕，在React应用程序中，所有的这些通常都表示为组件<br>例如：创建一个App呈现Welcome多次的组件 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">function Welcome(x){</span><br><span class="line"> return <h1>hello! {x.name}</h1>;</span><br><span class="line">}</span><br><span class="line">function App(){</span><br><span class="line"> return (</span><br><span class="line"> <div></span><br><span class="line"> <Welcome name ="1"/></span><br><span class="line"> <Welcome name ="2"/></span><br><span class="line"> <Welcome name ="3"/></span><br><span class="line"> </div></span><br><span class="line"> );</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">ReactDOM.render(</span><br><span class="line"> <App/>,</span><br><span class="line"> document.getElementById('root')</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<h3 id="提取组件"><a href="#提取组件" class="headerlink" title="提取组件"></a>提取组件</h3><p>不要害怕将组件分解成更小的组件</p>
<p>道具是只读的<br>无论将一个组件声明为一个函数还是一个类，它都不能修改它自己的道具。 </p>
<h2 id="状态和生命周期"><a href="#状态和生命周期" class="headerlink" title="状态和生命周期"></a>状态和生命周期</h2><p>更新UI的方法：使用它<code>ReactDOM.render()</code>改变呈现的输出： \</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">function tick(){</span><br><span class="line"> const element = (</span><br><span class="line"> <div></span><br><span class="line"> <h1>1</h1></span><br><span class="line"> <h2>It is {new Date().toLocaleTimeString()}.</h2></span><br><span class="line"> </div></span><br><span class="line"> );</span><br><span class="line"> ReactDOM.render(</span><br><span class="line"> element,</span><br><span class="line"> document.getElementById('root')</span><br><span class="line"> );</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">setInterval(tick,1000);</span><br></pre></td></tr></table></figure>
<p>封装时钟: </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">function Clock(props){</span><br><span class="line"> return(</span><br><span class="line"> <div></span><br><span class="line"> <h1>1</h1></span><br><span class="line"> <h2>It is {props.date.toLocaleTimeString()}</h2></span><br><span class="line"> </div></span><br><span class="line"> );</span><br><span class="line"> </span><br><span class="line"> function tick(){</span><br><span class="line"> ReactDOM.render(</span><br><span class="line"> <Clock date={new Date()}/>,</span><br><span class="line"> document.getElementById('root')</span><br><span class="line"> );</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">setInterval(tick,1000);</span><br></pre></td></tr></table></figure>
<p>给组件添加“状态”，状态类似于道具，是私人的并且是完全由组件控制的。 </p>
<h3 id="将函数转换为类"><a href="#将函数转换为类" class="headerlink" title="将函数转换为类"></a>将函数转换为类</h3><p>1.创建一个扩展名为ES6的类，名称相同的React.Component<br>2.为它添加一个空的方法render()<br>3.将函数的主体移动到render方法中<br>4.更换props用this.props的render身体<br>5.删除多余的空函数声明 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">class Clock extends React.Component{</span><br><span class="line"> render(){</span><br><span class="line"> return(</span><br><span class="line"> <div></span><br><span class="line"> <h1>1</h1></span><br><span class="line"> <h2>It is {this.props.date.toLocaleTimeString()}.</h2></span><br><span class="line"> </div></span><br><span class="line"> )</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>将本地状态添加到类 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">class Clock extends React.Component{</span><br><span class="line"> constuctor(props){</span><br><span class="line"> super(props);</span><br><span class="line"> this.state = {date: new Date()};</span><br><span class="line"> }</span><br><span class="line"> render(){</span><br><span class="line"> return(</span><br><span class="line"> <div></span><br><span class="line"> <h1>2</h1></span><br><span class="line"> <h2> It is {this.state.date.toLocaleTimeString()}.</h2></span><br><span class="line"> </div></span><br><span class="line"> );</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">ReactDOM.render(</span><br><span class="line"><Clock />,</span><br><span class="line">document.getElementById('root')</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<p>接下来设置计时器每秒更新一次</p>
<h3 id="将生命周期方法添加到类中"><a href="#将生命周期方法添加到类中" class="headerlink" title="将生命周期方法添加到类中"></a>将生命周期方法添加到类中</h3><p>一个组件完整的生命周期(<code>lifecycle hooks</code>)包括实例化阶段、活动阶段、销毁阶段，每个阶段又由相应的方法管理<br><code>mounting</code> :表示正在挂载虚拟DOM到真实DOM<br><code>updating</code> :表示正被重新渲染<br><code>unmounting</code>:表示正在将虚拟DOM移除真实DOM</p>
<p>每个过程提供了两个函数</p>
<p><code>componentWillMount()</code><br><code>componentDidMount()</code><br><code>componentWillUpdate(object nextProps,object nextState)</code><br><code>componentDidUpdate(object nextProps,object nextState)</code><br><code>componentWillUnmount()</code> </p>
<p><code>componentDidMount()</code> 在组件输出呈现给DOM后，该钩子运行，是设置定时器的好地方 </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">componentDidMount(){</span><br><span class="line"> this.timerID = setInterval(</span><br><span class="line"> () => this.tick(),1000</span><br><span class="line"> );</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">compoentWillUnmount(){</span><br><span class="line"> clearInterval(this.timerID);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>最终： </p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><span class="line">class Clock extends React.Component{</span><br><span class="line"> constuctor(props){</span><br><span class="line"> super(props);</span><br><span class="line"> this.state = {date: new Date()};</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> componentDidMount(){</span><br><span class="line"> this.timerID = setInterval(</span><br><span class="line"> () => this.tick(),1000</span><br><span class="line"> );</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> compoentWillUnmount(){</span><br><span class="line"> clearInterval(this.timerID);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> tick(){</span><br><span class="line"> this.setState({</span><br><span class="line"> date:new Date()</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> render(){</span><br><span class="line"> return(</span><br><span class="line"> <div></span><br><span class="line"> <h1>2</h1></span><br><span class="line"> <h2> It is {this.state.date.toLocaleTimeString()}.</h2></span><br><span class="line"> </div></span><br><span class="line"> );</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">ReactDOM.render(</span><br><span class="line"> <Clock />,</span><br><span class="line"> document.getElementById('root')</span><br><span class="line">);</span><br></pre></td></tr></table></figure>
<h3 id="正确使用状态（State）"><a href="#正确使用状态（State）" class="headerlink" title="正确使用状态（State）"></a>正确使用状态（State）</h3><p>setState()来改变状态，状态的更新可能是异步的</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">this.setState(function(prevState,props){</span><br><span class="line"> return{</span><br><span class="line"> counter:pervState.counter + props.increment</span><br><span class="line"> };</span><br><span class="line">});</span><br></pre></td></tr></table></figure>
<p>参考链接：<a href="https://react.docschina.org/docs/hello-world.html">https://react.docschina.org/docs/hello-world.html</a></p>
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