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aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithHideOnScrollNavbar_3R7-" id="知识点深入"></a>知识点深入<a class="hash-link" href="#知识点深入" title="Direct link to heading">#</a></h2><h3><a aria-hidden="true" tabindex="-1" class="anchor anchor__h3 anchorWithHideOnScrollNavbar_3R7-" id="1-new-操作符做了什么"></a>1. new 操作符做了什么<a class="hash-link" href="#1-new-操作符做了什么" title="Direct link to heading">#</a></h3><ol><li>在内存中创建一个新对象。</li><li>将新对象内部的 __proto__ 赋值为构造函数的 prototype 属性。</li><li>将构造函数内部的 this 被赋值为新对象（即 this 指向新对象）。</li><li>执行构造函数内部的代码（给新对象添加属性）。</li><li>如果构造函数返回非空对象，则返回该对象。否则返回 this。</li></ol><h3><a aria-hidden="true" tabindex="-1" class="anchor anchor__h3 anchorWithHideOnScrollNavbar_3R7-" id="2-new-操作符的模拟实现"></a>2. new 操作符的模拟实现<a class="hash-link" href="#2-new-操作符的模拟实现" title="Direct link to heading">#</a></h3><div class="codeBlockContainer_K1bP"><div class="codeBlockContent_hGly js"><pre tabindex="0" class="prism-code language-js codeBlock_23N8 thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_39YC"><span class="token-line" style="color:#393A34"><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">fakeNew</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 创建新对象</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">var</span><span class="token plain"> obj </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token known-class-name class-name">Object</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">create</span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword null nil" style="color:#00009f">null</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">var</span><span class="token plain"> </span><span class="token maybe-class-name">Constructor</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">[</span><span class="token punctuation" style="color:#393A34">]</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">shift</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">call</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">arguments</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 将对象的 __proto__ 赋值为构造函数的 prototype 属性</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> obj</span><span class="token punctuation" style="color:#393A34">.</span><span class="token property-access">__proto__</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token class-name">Constructor</span><span class="token punctuation" style="color:#393A34">.</span><span class="token property-access">prototype</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 将构造函数内部的 this 赋值为新对象</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">var</span><span class="token plain"> ret </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token maybe-class-name">Constructor</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">apply</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">obj</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> arguments</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 返回新对象</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword control-flow" style="color:#00009f">return</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">typeof</span><span class="token plain"> ret </span><span class="token operator" style="color:#393A34">===</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"object"</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">&&</span><span class="token plain"> ret </span><span class="token operator" style="color:#393A34">!==</span><span class="token plain"> </span><span class="token keyword null nil" style="color:#00009f">null</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">?</span><span class="token plain"> ret </span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> obj</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block">
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</span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function maybe-class-name" style="color:#d73a49">Group</span><span class="token punctuation" style="color:#393A34">(</span><span class="token parameter">name</span><span class="token parameter punctuation" style="color:#393A34">,</span><span class="token parameter"> member</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token property-access">name</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> name</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token property-access">member</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> member</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block">
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</span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">var</span><span class="token plain"> group </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">fakeNew</span><span class="token punctuation" style="color:#393A34">(</span><span class="token maybe-class-name">Group</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"hzfe"</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">17</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">;</span></span></code></pre><button type="button" aria-label="Copy code to clipboard" class="copyButton_Ue-o clean-btn">Copy</button></div></div><h2><a aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithHideOnScrollNavbar_3R7-" id="参考资料"></a>参考资料<a class="hash-link" href="#参考资料" title="Direct link to heading">#</a></h2><ol><li><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/new" target="_blank" rel="noopener noreferrer">new 操作符 - MDN</a></li><li><a href="https://262.ecma-international.org/5.1/#sec-11.2.2" target="_blank" rel="noopener noreferrer">The new Operator</a></li></ol></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><div class="pagination-nav__item"><a class="pagination-nav__link" href="/awesome-interview/book2/js-inherite"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">« 基础：ES5、ES6 如何实现继承</div></a></div><div class="pagination-nav__item pagination-nav__item--next"><a class="pagination-nav__link" href="/awesome-interview/book2/css-preprocessor"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">样式：谈谈 CSS 预处理器 »</div></a></div></nav></div></div><div class="col col--3"><div class="tableOfContents_35-E thin-scrollbar"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#相关问题" class="table-of-contents__link">相关问题</a></li><li><a href="#回答关键点" class="table-of-contents__link">回答关键点</a></li><li><a href="#知识点深入" class="table-of-contents__link">知识点深入</a><ul><li><a href="#1-new-操作符做了什么" class="table-of-contents__link">1. new 操作符做了什么</a></li><li><a href="#2-new-操作符的模拟实现" class="table-of-contents__link">2. new 操作符的模拟实现</a></li></ul></li><li><a href="#参考资料" class="table-of-contents__link">参考资料</a></li></ul></div></div></div><div class="row"><div class="col"><div class="react-utterences"><div>Loading script...</div></div></div><div class="col col--3"></div></div></div></main></div></div></div>
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