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class="sidebar-link">State&生命周期</a></li><li><a href="/blog/pages/f27775/" aria-current="page" class="active sidebar-link">事件处理</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level2"><a href="/blog/pages/f27775/#与传统html绑定事件的区别" class="sidebar-link">与传统HTML绑定事件的区别</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/blog/pages/f27775/#阻止默认事件-合成事件对象" class="sidebar-link">阻止默认事件 (合成事件对象)</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/blog/pages/f27775/#绑定事件的方式" class="sidebar-link">绑定事件的方式</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/blog/pages/f27775/#事件命名规范" class="sidebar-link">事件命名规范</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/blog/pages/f27775/#向事件处理程序传递参数" class="sidebar-link">向事件处理程序传递参数</a></li></ul></li><li><a href="/blog/pages/8fcda8/" class="sidebar-link">条件渲染</a></li><li><a href="/blog/pages/88f4b0/" class="sidebar-link">列表&Key</a></li><li><a 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href="/blog/" title="首页" class="iconfont icon-home router-link-active" data-v-06970110></a></li> <li data-v-06970110><a href="/blog/note/react/#《React》笔记" data-v-06970110>《React》笔记</a></li><li data-v-06970110><a href="/blog/note/react/#核心概念" data-v-06970110>核心概念</a></li></ul> <div class="info" data-v-06970110><div title="作者" class="author iconfont icon-touxiang" data-v-06970110><a href="https://github.com/heBody" target="_blank" title="作者" class="beLink" data-v-06970110>heBody</a></div> <div title="创建时间" class="date iconfont icon-riqi" data-v-06970110><a href="javascript:;" data-v-06970110>2021-03-24</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="data:image/png;base64,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">事件处理<!----></h1> <div class="theme-vdoing-content content__default"><h1 id="_05-事件处理"><a href="#_05-事件处理" class="header-anchor">#</a> 05. 事件处理</h1> <h2 id="与传统html绑定事件的区别"><a href="#与传统html绑定事件的区别" class="header-anchor">#</a> 与传统HTML绑定事件的区别</h2> <p>传统的 HTML：</p> <div class="language-html line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token special-attr"><span class="token attr-name">onclick</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span><span class="token value javascript language-javascript"><span class="token function">activateLasers</span><span class="token punctuation">(</span><span class="token punctuation">)</span></span><span class="token punctuation">"</span></span></span><span class="token punctuation">></span></span>
- Activate Lasers
- <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>在 React 中略微不同：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token comment">// 1.事件名为小驼峰； 2.传入函数以大括号包裹函数名形式</span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span>activateLasers<span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">
- Activate Lasers
- </span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><ul><li>React 事件的命名采用小驼峰式（camelCase），而不是纯小写。</li> <li>使用 JSX 语法时你需要传入一个函数作为事件处理函数，而不是一个字符串。</li></ul> <h3 id="阻止默认事件-合成事件对象"><a href="#阻止默认事件-合成事件对象" class="header-anchor">#</a> 阻止默认事件 (合成事件对象)</h3> <p>在 React 中，你需要这样阻止默认事件：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token keyword">function</span> <span class="token function">ActionLink</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
- <span class="token keyword">function</span> <span class="token function">handleClick</span><span class="token punctuation">(</span><span class="token parameter">e</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
- e<span class="token punctuation">.</span><span class="token function">preventDefault</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
- console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">'The link was clicked.'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- <span class="token keyword">return</span> <span class="token punctuation">(</span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>a</span> <span class="token attr-name">href</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">"</span>#<span class="token punctuation">"</span></span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span>handleClick<span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">
- Click me
- </span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>a</span><span class="token punctuation">></span></span>
- <span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><p>在这里，<code>e</code> 是一个<strong>合成事件</strong>。React 根据 <a href="https://www.w3.org/TR/DOM-Level-3-Events/" target="_blank" rel="noopener noreferrer">W3C 规范<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>来定义这些合成事件，所以你不需要担心跨浏览器的兼容性问题。React 事件与原生事件不完全相同。如果想了解更多，请查看 <a href="https://zh-hans.reactjs.org/docs/events.html" target="_blank" rel="noopener noreferrer"><code>SyntheticEvent</code><span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 参考指南。</p> <h2 id="绑定事件的方式"><a href="#绑定事件的方式" class="header-anchor">#</a> 绑定事件的方式</h2> <p>使用 React 时，你一般不需要使用 <code>addEventListener</code> 为已创建的 DOM 元素添加监听器。事实上，你只需要在该元素初始渲染的时候添加监听器即可。</p> <p>当你使用 <a href="https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Classes" target="_blank" rel="noopener noreferrer">ES6 class<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 语法定义一个组件的时候，通常的做法是将事件处理函数声明为 class 中的方法。例如，下面的 <code>Toggle</code> 组件会渲染一个让用户切换开关状态的按钮：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token keyword">class</span> <span class="token class-name">Toggle</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span>
- <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">props</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
- <span class="token keyword">super</span><span class="token punctuation">(</span>props<span class="token punctuation">)</span>
- <span class="token keyword">this</span><span class="token punctuation">.</span>state <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token literal-property property">isToggleOn</span><span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
- <span class="token comment">// 为了在回调中使用 `this`，这个绑定是必不可少的</span>
- <span class="token keyword">this</span><span class="token punctuation">.</span>handleClick <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">handleClick</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span>；
- <span class="token punctuation">}</span>
- <span class="token function">hadleClick</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
- <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token parameter">state</span> <span class="token operator">=></span> <span class="token punctuation">(</span><span class="token punctuation">{</span>
- <span class="token literal-property property">isToggleOn</span><span class="token operator">:</span> <span class="token operator">!</span>state<span class="token punctuation">.</span>isToggleOn
- <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
- <span class="token keyword">return</span><span class="token punctuation">(</span>
- <span class="token comment">// 为了能在这里使用 this.handleClick调用方法，因此需要在构造函数内添加handleChick属性指向回调方法 ？</span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>handleClick<span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">
- </span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>isToggleOn <span class="token operator">?</span> <span class="token string">'ON'</span> <span class="token operator">:</span> <span class="token string">'OFF'</span><span class="token punctuation">}</span><span class="token plain-text">
- </span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- <span class="token punctuation">)</span>
- <span class="token punctuation">}</span>
- <span class="token punctuation">}</span>
- ReactDOM<span class="token punctuation">.</span><span class="token function">render</span><span class="token punctuation">(</span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span><span class="token class-name">Toggle</span></span> <span class="token punctuation">/></span></span><span class="token punctuation">,</span>
- document<span class="token punctuation">.</span><span class="token function">getElementById</span><span class="token punctuation">(</span><span class="token string">'root'</span><span class="token punctuation">)</span>
- <span class="token punctuation">)</span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br></div></div><p>你必须谨慎对待 JSX 回调函数中的 <code>this</code>，在 JavaScript 中，class 的方法默认不会<a href="https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_objects/Function/bind" target="_blank" rel="noopener noreferrer">绑定<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> <code>this</code>。如果你忘记绑定 <code>this.handleClick</code> 并把它传入了 <code>onClick</code>，当你调用这个函数的时候 <code>this</code> 的值为 <code>undefined</code>。</p> <p>这并不是 React 特有的行为；这其实与 <a href="https://www.smashingmagazine.com/2014/01/understanding-javascript-function-prototype-bind/" target="_blank" rel="noopener noreferrer">JavaScript 函数工作原理<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>有关。通常情况下，如果你没有在方法后面添加 <code>()</code>，例如 <code>onClick={this.handleClick}</code>，你应该<strong>为这个方法绑定 <code>this</code></strong>。</p> <p>如果觉得使用 <code>bind</code> 很麻烦，这里有两种方式可以解决。如果你正在使用实验性的 <a href="https://babeljs.io/docs/plugins/transform-class-properties/" target="_blank" rel="noopener noreferrer">public class fields 语法<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>，你可以使用 class fields 正确的绑定回调函数：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token keyword">class</span> <span class="token class-name">LoggingButton</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span>
- <span class="token comment">// 此语法确保 `handleClick` 内的 `this` 已被绑定。</span>
- <span class="token comment">// 注意: 这是 *实验性* 语法。</span>
- <span class="token function-variable function">handleClick</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
- console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">'this is:'</span><span class="token punctuation">,</span> <span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
- <span class="token keyword">return</span> <span class="token punctuation">(</span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>handleClick<span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">
- Click me
- </span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- <span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- <span class="token punctuation">}</span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><p><a href="https://github.com/facebookincubator/create-react-app" target="_blank" rel="noopener noreferrer">Create React App<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 默认启用此语法。</p> <p>如果你没有使用 class fields 语法，你可以在回调中使用<a href="https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/Arrow_functions" target="_blank" rel="noopener noreferrer">箭头函数<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token keyword">class</span> <span class="token class-name">LoggingButton</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span>
- <span class="token function">handleClick</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
- console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">'this is:'</span><span class="token punctuation">,</span> <span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
- <span class="token comment">// 此语法确保 `handleClick` 内的 `this` 已被绑定。</span>
- <span class="token keyword">return</span> <span class="token punctuation">(</span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">handleClick</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">
- Click me
- </span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- <span class="token punctuation">)</span><span class="token punctuation">;</span>
- <span class="token punctuation">}</span>
- <span class="token punctuation">}</span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><p>此语法问题在于每次渲染 <code>LoggingButton</code> 时都会创建不同的回调函数。在大多数情况下，这没什么问题，但如果该回调函数作为 prop 传入子组件时，这些组件可能会进行额外的重新渲染。<strong>我们通常建议在构造器中绑定或使用 class fields 语法来避免这类性能问题</strong>。</p> <h3 id="事件命名规范"><a href="#事件命名规范" class="header-anchor">#</a> 事件命名规范</h3> <p>在 React 中，有一个命名规范，通常会将代表事件的监听 prop 命名为 <code>on[Event]</code>，将处理事件的监听方法命名为 <code>handle[Event]</code> 这样的格式。</p> <h2 id="向事件处理程序传递参数"><a href="#向事件处理程序传递参数" class="header-anchor">#</a> 向事件处理程序传递参数</h2> <p>在循环中，通常我们会为事件处理函数传递额外的参数。例如，若 <code>id</code> 是你要删除那一行的 ID，以下两种方式都可以向事件处理函数传递参数：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token punctuation">(</span><span class="token parameter">e</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">deleteRow</span><span class="token punctuation">(</span>id<span class="token punctuation">,</span> e<span class="token punctuation">)</span><span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">Delete Row</span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">deleteRow</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">,</span> id<span class="token punctuation">)</span><span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">Delete Row</span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span>
- </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>上述两种方式是等价的，分别通过<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions" target="_blank" rel="noopener noreferrer">箭头函数<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>和 <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_objects/Function/bind" target="_blank" rel="noopener noreferrer"><code>Function.prototype.bind</code><span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 来实现。</p> <p>在这两种情况下，<strong>React 的事件对象 <code>e</code> 会被作为第二个参数传递</strong>。如果通过箭头函数的方式，事件对象必须显式的进行传递，而通过 <code>bind</code> 的方式，事件对象以及更多的参数将会被隐式的进行传递。</p></div></div> <div class="page-edit"><div class="edit-link"><a href="https://github.com/heBody/blog/edit/master/docs/《React》笔记/01.核心概念/05.事件处理.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <div class="tags"><a href="/blog/tags/?tag=React" title="标签">#React</a></div> <div class="last-updated"><span class="prefix">上次更新:</span> <span class="time">2022/12/14, 19:36:42</span></div></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/blog/pages/1e3ca2/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">State&生命周期</div></a> <a href="/blog/pages/8fcda8/" class="page-nav-centre page-nav-centre-next"><div class="tooltip">条件渲染</div></a></div> <div class="page-nav"><p class="inner"><span class="prev">
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