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link" href="/note/JavaScript.html" data-v-66b47b62 data-v-8dd200cc><!--[--><p class="text" data-v-66b47b62>JavaScript基础</p><!--]--><!----></a><div class="caret" role="button" data-v-66b47b62><!----></div></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-66b47b62 data-v-66b47b62><div class="item" data-v-66b47b62><div class="indicator" data-v-66b47b62></div><a class="VPLink link link" href="/note/CSS.html" data-v-66b47b62 data-v-8dd200cc><!--[--><p class="text" data-v-66b47b62>CSS基础</p><!--]--><!----></a><div class="caret" role="button" data-v-66b47b62><!----></div></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-66b47b62 data-v-66b47b62><div class="item" data-v-66b47b62><div class="indicator" data-v-66b47b62></div><a class="VPLink link link" href="/note/JavaScriptEnhanced.html" data-v-66b47b62 data-v-8dd200cc><!--[--><p class="text" data-v-66b47b62>JavaScript进阶</p><!--]--><!----></a><div class="caret" role="button" data-v-66b47b62><!----></div></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-66b47b62 data-v-66b47b62><div class="item" data-v-66b47b62><div class="indicator" data-v-66b47b62></div><a class="VPLink link link" href="/note/Front-end%20Engineering.html" data-v-66b47b62 data-v-8dd200cc><!--[--><p class="text" data-v-66b47b62>前端工程化</p><!--]--><!----></a><div class="caret" role="button" data-v-66b47b62><!----></div></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-66b47b62 data-v-66b47b62><div class="item" data-v-66b47b62><div class="indicator" data-v-66b47b62></div><a class="VPLink link link" href="/note/SSR.html" data-v-66b47b62 data-v-8dd200cc><!--[--><p class="text" data-v-66b47b62>服务端渲染</p><!--]--><!----></a><div class="caret" role="button" data-v-66b47b62><!----></div></div><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-3af881ed data-v-e31feb0e><div class="VPDoc has-sidebar has-aside" data-v-e31feb0e data-v-30dabfe4><div class="container" data-v-30dabfe4><div class="aside" data-v-30dabfe4><div class="aside-curtain" data-v-30dabfe4></div><div class="aside-container" data-v-30dabfe4><div class="aside-content" data-v-30dabfe4><div class="VPDocAside" data-v-30dabfe4 data-v-7110f5c9><!--[--><!--]--><!--[--><!--]--><div class="VPDocAsideOutline" data-v-7110f5c9 data-v-9c6f1a55><div class="content" data-v-9c6f1a55><div class="outline-marker" data-v-9c6f1a55></div><div class="outline-title" data-v-9c6f1a55>On this page</div><nav aria-labelledby="doc-outline-aria-label" data-v-9c6f1a55><span class="visually-hidden" id="doc-outline-aria-label" data-v-9c6f1a55> Table of Contents for current page </span><ul class="root" data-v-9c6f1a55 data-v-02afc12d><!--[--><!--]--></ul></nav></div></div><!--[--><!--]--><div class="spacer" data-v-7110f5c9></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--]--></div></div></div></div><div class="content" data-v-30dabfe4><div class="content-container" data-v-30dabfe4><!--[--><!--]--><main class="main" data-v-30dabfe4><div style="position:relative;" class="vp-doc _article_%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3Proxy%E4%B8%8EReflect" data-v-30dabfe4><div><h1 id="深入理解proxy与reflect" tabindex="-1">深入理解Proxy与Reflect <a class="header-anchor" href="#深入理解proxy与reflect" aria-hidden="true">#</a></h1><h3 id="监听对象的操作" tabindex="-1">监听对象的操作 <a class="header-anchor" href="#监听对象的操作" aria-hidden="true">#</a></h3><p>可以使用Proxy对象将原对象包裹，此后的操作都对<code>proxy</code>进行，每次<code>get</code>与<code>set</code>被触发时都会自动执行相应代码</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> obj </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">age</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">18</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1.88</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">get</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">get</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">target</span><span style="color:#F07178;">[</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">set</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">value</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">set</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">value</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">target</span><span style="color:#F07178;">[</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">] </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">value</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> tmp </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> proxy</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">height </span><span style="color:#676E95;font-style:italic;">// getter被触发</span></span>
<span class="line"><span style="color:#A6ACCD;">proxy</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// setter被触发</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>除此之外，在之前的版本中可以通过<code>Object.defineProperty</code>为对象中某个属性设置<code>getter</code>与<code>setter</code>函数，可以达到类似的效果</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#89DDFF;font-style:italic;">for</span><span style="color:#A6ACCD;"> (</span><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> key </span><span style="color:#89DDFF;">of</span><span style="color:#A6ACCD;"> Object</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">keys</span><span style="color:#A6ACCD;">(obj)) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">let</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">value</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">obj</span><span style="color:#F07178;">[</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Object</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">defineProperty</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">obj</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> get</span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">get</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">value</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">value</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#F07178;"> set</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">newVal</span><span style="color:#89DDFF;">)</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">set</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">value</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><p>但是通过<code>Object.defineProperty</code>实现的监听存在问题：</p><ul><li><code>Object.defineProperty</code>设计之初并不是为了监听一个对象中的所有属性的</li><li>如果要监听新增/删除属性，那么此时<code>Object.defineProperty</code>是无能为力的</li></ul><h3 id="proxy类基本使用" tabindex="-1">Proxy类基本使用 <a class="header-anchor" href="#proxy类基本使用" aria-hidden="true">#</a></h3><div class="language-JS line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">JS</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> handler)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>即使不传入handler，默认也会进行基本的代理操作</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> obj </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">age</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">18</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"><span style="color:#A6ACCD;">proxy</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">height </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1.88</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 添加新属性</span></span>
<span class="line"><span style="color:#A6ACCD;">proxy</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 修改原属性</span></span>
<span class="line"></span>
<span class="line"><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#A6ACCD;">(obj) </span><span style="color:#676E95;font-style:italic;">// { name: &#39;Ziu&#39;, age: 18, height: 1.88 }</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><h3 id="捕获器" tabindex="-1">捕获器 <a class="header-anchor" href="#捕获器" aria-hidden="true">#</a></h3><p>常用的捕获器有<code>set</code>与<code>get</code>函数</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">set</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">newVal</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 设置 </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">newVal</span><span style="color:#89DDFF;">}`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">target</span><span style="color:#F07178;">[</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">] </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">get</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 获取</span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">target</span><span style="color:#F07178;">[</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><ul><li>set函数有四个参数 <ul><li>target 目标对象（侦听的对象）</li><li>property 即将被设置的属性key</li><li>value 新属性值</li><li>receiver 调用的代理对象</li></ul></li><li>get函数有三个参数 <ul><li>target 目标对象（侦听的对象）</li><li>property 被获取的属性key</li><li>receiver 调用的代理对象</li></ul></li></ul><p>另外介绍两个捕获器：<code>has</code>与<code>deleteProperty</code></p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">...</span></span>
<span class="line"><span style="color:#A6ACCD;"> has: </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 判断</span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">in</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">target</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">deleteProperty</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 删除 </span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#FF9CAC;">true</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">delete</span><span style="color:#A6ACCD;"> proxy</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name </span><span style="color:#676E95;font-style:italic;">// 监听: name 删除</span></span>
<span class="line"><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">age</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">in</span><span style="color:#A6ACCD;"> proxy) </span><span style="color:#676E95;font-style:italic;">// 监听: age 判断</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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><h3 id="reflect" tabindex="-1">Reflect <a class="header-anchor" href="#reflect" aria-hidden="true">#</a></h3><p>Reflect是ES6新增的一个API，它本身是一个对象</p><ul><li>提供了很多操作JavaScript对象的方法，有点像Object中操作对象的方法</li><li>比如<code>Reflect.getPrototypeOf(target)</code>类似于<code>Object.getPrototypeOf()</code></li><li>比如<code>Reflect.defineProperty(targetm propertyKey, attributes)</code>类似于<code>Object.defineProperty()</code></li></ul><p>如果我们又Object对象可以完成这些操作，为什么还需要Reflect呢？</p><ul><li>Object作为一个构造函数，这些操作放到它身上并不合适</li><li>包含一些类似于 in delete的操作符</li><li>在ES6新增了Reflect，让这些操作都集中到了Reflect对象上</li><li>在使用Proxy时，可以做到不操作原对象</li></ul><h3 id="与object的区别" tabindex="-1">与Object的区别 <a class="header-anchor" href="#与object的区别" aria-hidden="true">#</a></h3><p>删除对象上的某个属性</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> obj </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">age</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">18</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 当且仅当该属性的 configurable 键值为 true 时，该属性的描述符才能够被改变</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 同时该属性也能从对应的对象上被删除。 默认为 false。</span></span>
<span class="line"><span style="color:#A6ACCD;">Object</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">defineProperty</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">name</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">configurable</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#FF9CAC;">false</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 1. 旧方法 检查`delete obj.name`是否执行成功</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 结果: 需要额外编写检查代码且存在问题(严格模式下删除configurable为false的属性将报错)</span></span>
<span class="line"><span style="color:#89DDFF;">delete</span><span style="color:#A6ACCD;"> obj</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">if</span><span style="color:#A6ACCD;"> (obj</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#FF9CAC;">false</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">else</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#FF9CAC;">true</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 2. Reflect</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 结果: 根据是否删除成功返回结果</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">if</span><span style="color:#A6ACCD;"> (Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">deleteProperty</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">name</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;">)) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#FF9CAC;">true</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">else</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#FF9CAC;">false</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><h3 id="reflect常见方法" tabindex="-1">Reflect常见方法 <a class="header-anchor" href="#reflect常见方法" aria-hidden="true">#</a></h3><p>其中的方法与Proxy的方法是一一对应的，一共13个。其中的一些方法是Object对象中没有的：</p><ul><li><code>has</code> 判断一个对象是否存在某个属性，和 <code>in</code> 运算符功能完全相同</li><li><code>get</code> 获取对象身上某个属性的值，类似于<code>target[key]</code></li><li><code>set</code> 将值分配给属性的函数，返回一个Boolean，如果更新成功则返回true</li><li><code>deleteProperty</code> 作为函数的 <code>delete</code> 操作符，相当于执行 <code>delete target[key]</code></li><li>···</li></ul><p>代理对象的目的：不再直接操作原始对象，一切读写操作由代理完成。我们先前在编写Proxy的代理代码时，仍然有操作原对象的行为：</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">set</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">newVal</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 设置 </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">newVal</span><span style="color:#89DDFF;">}`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">target</span><span style="color:#F07178;">[</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">] </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span><span style="color:#F07178;"> </span><span style="color:#676E95;font-style:italic;">// 直接操作原对象</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><p>这时我们可以让Reflect登场，代替我们对原对象进行操作，之前的代码可以修改：</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">set</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">newVal</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 设置 </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">newVal</span><span style="color:#89DDFF;">}`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">set</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">get</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 获取</span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">get</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">has</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 判断</span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">has</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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>使用Reflect替代之前的对象操作有以下好处：</p><ul><li>代理对象的目的：不再直接操作原对象</li><li>Reflect.set方法有返回Boolean值，可以判断本次操作是否成功</li><li>receiver就是外层的Proxy对象</li></ul><p>针对好处三，做出如下解释。以下述代码为例，<code>set name(){}</code>函数中的<code>this</code>指向的是<code>obj</code></p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> obj </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">_name</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">set</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">newVal</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">set name </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">newVal</span><span style="color:#89DDFF;">}`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">this</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">_name</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">get</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">get name</span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">this</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">_name</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name)</span></span>
<span class="line"><span style="color:#A6ACCD;">obj</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">name </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Ziu</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> proxy </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Proxy</span><span style="color:#A6ACCD;">(obj</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">set</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">newVal</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">receiver</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 设置 </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">newVal</span><span style="color:#89DDFF;">}`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">set</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">newVal</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">receiver</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">get</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">target</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">key</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">receiver</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">`</span><span style="color:#C3E88D;">监听: </span><span style="color:#89DDFF;">${</span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">}</span><span style="color:#C3E88D;"> 获取</span><span style="color:#89DDFF;">`</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">get</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">key</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">receiver</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><p>我们使用Proxy代理，并且使用Reflect操作对象时，输出的<code>this</code>仍然为<code>obj</code>，需要注意的是，此处的<code>this</code>指向是默认指向原始对象<code>obj</code>，而如果业务需要改变<code>this</code>指向，此时可以为<code>Reflect.set()</code>的最后一个参数传入<code>receiver</code></p><h3 id="reflect-construct方法" tabindex="-1">Reflect.construct方法 <a class="header-anchor" href="#reflect-construct方法" aria-hidden="true">#</a></h3><p>以下两段代码的实现结果是一样的：</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Person</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">name</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">age</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">name</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">name</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">age</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">age</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Student</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">name</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">age</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">Person</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">call</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">this,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">name</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">age</span><span style="color:#F07178;">) </span><span style="color:#676E95;font-style:italic;">// 借用</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> stu </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Student</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">18</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#A6ACCD;">(stu)</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><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></div></div><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Person</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">name</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">age</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">name</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">name</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">age</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">age</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Student</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">name</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">age</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#89DDFF;"> </span><span style="color:#676E95;font-style:italic;">// Person.call(this, name, age) // 借用</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> stu </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> Reflect</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">construct</span><span style="color:#A6ACCD;">(Person</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> [</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">18</span><span style="color:#A6ACCD;">]</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> Student)</span></span>
<span class="line"><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#A6ACCD;">(stu)</span></span>
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