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<h1>Yolanda的随手记<span class="blink-fast">∎</span></h1>
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<a href="/2022/11/24/My-First-Post/" >手写简易版webpack</a>
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<div class="date">post @ 2022-11-24 </div>
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<h2 id="明确-webpack-实现的功能"><a href="#明确-webpack-实现的功能" class="headerlink" title="明确 webpack 实现的功能"></a>明确 webpack 实现的功能</h2><blockquote>
<p>本质上，webpack 是一个现代 JavaScript 应用程序的静态模块打包器(module bundler)。 当 webpack 处理应用程序时，它会递归地构建一个依赖关系图(dependency graph)，其中包含应用程序需要的每个模块，然后将所有这些模块打包成一个或多个 bundle。</p>
</blockquote>
<p><strong>我们的代码主要实现以下四步</strong></p>
<figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">A(1.找到入口文件)</span><br><span class="line">B(2.解析入口文件并提取出依赖)</span><br><span class="line">C(3.递归创造出依赖图)</span><br><span class="line">D(4.把所有文件打包成一个文件)</span><br></pre></td></tr></table></figure>
<h2 id="开始开发"><a href="#开始开发" class="headerlink" title="开始开发"></a>开始开发</h2><p>** 1.目录下新建三个 js 源文件 **</p>
<ul>
<li>entry.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> message <span class="keyword">from</span> <span class="string">"./message.js"</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(message);</span><br></pre></td></tr></table></figure>
<ul>
<li>message.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> name <span class="keyword">from</span> <span class="string">"./name.js"</span>;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> <span class="string">`<span class="subst">${name}</span> is a girl`</span>;</span><br></pre></td></tr></table></figure>
<ul>
<li>name.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">export</span> <span class="keyword">const</span> name = <span class="string">"Yolanda"</span>;</span><br></pre></td></tr></table></figure>
<p>梳理下依赖关系，我们的入口文件是 entry.js，entry 依赖 message，message 依赖 name。</p>
<p><strong>2.新建一个 mywebpack.js 文件，首先读取一下 entry 入口文件中的内容。</strong><br>读取文件需要用到 node 的一个基础 api-fs(文件系统),fs.readFileSync 可以同步拿到 js 文件中的代码内容。</p>
<ul>
<li>mywebpack.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">const</span> fs = <span class="built_in">require</span>(<span class="string">"fs"</span>);</span><br><span class="line"><span class="keyword">function</span> <span class="title function_">creatAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"> <span class="variable language_">console</span>.<span class="title function_">log</span>(content);</span><br><span class="line">}</span><br><span class="line"><span class="title function_">creatAsset</span>(<span class="string">"./source/entry.js"</span>);</span><br></pre></td></tr></table></figure>
<p>在当前目录下运行一下命令, 看一下输出<br><code>node mywebpack.js</code></p>
<p>输出内容为 entry.js 中的代码：</p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> message <span class="keyword">from</span> <span class="string">"./message.js"</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(message);</span><br></pre></td></tr></table></figure>
<p><strong>3. 分析 ast,思考如何解析出 entry.js 文件中的依赖</strong><br>可以使用 ast 工具 <a target="_blank" rel="noopener" href="https://astexplorer.net/">https://astexplorer.net/</a><br>看一下 entry.js 文件的 ast 是什么？</p>
<p>3.1 可以看到最上级是一个 File, File 中包含换一个 program, 就是我们的程序<br>3.2 在 program 的 body 属性里, 就是我们各种语法的描述<br>3.3 可以看到第一个就是 ImportDeclaration, 也就是引入的声明.<br>3.4 ImportDeclaration 里有一个 source 属性, 它的 value 就是引入的文件地址 ‘./message.js’</p>
<p><strong>4.生成 entry.js 的 ast</strong><br>首先安装一个 Babylon(基于 Babel 的 js 解析工具)<br><code>npm i babylon</code></p>
<ul>
<li>mywebpack.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">const</span> fs = <span class="built_in">require</span>(<span class="string">"fs"</span>);</span><br><span class="line"><span class="keyword">const</span> babylon = <span class="built_in">require</span>(<span class="string">"babylon"</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">createAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> ast = babylon.<span class="title function_">parse</span>(content, {</span><br><span class="line"> <span class="attr">sourceType</span>: <span class="string">"module"</span>,</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="variable language_">console</span>.<span class="title function_">log</span>(ast);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="title function_">createAsset</span>(<span class="string">"./source/entry.js"</span>);</span><br></pre></td></tr></table></figure>
<p>可以看到输出了一个 Object, 这就是咱们 entry.js 的 AST.</p>
<p><strong>5.基于这个 ast，找到 entry.js 的 ImportDeclaration 中的 source.value</strong><br>首先，需要遍历出 ImportDeclaration 节点，那就需要一个工具：babel-traverse(可以像遍历对象一样遍历 ast 中的节点)<br><code>npm i babel-traverse</code><br>然后利用它遍历并获取到对应节点，提供一个函数来操作此节点。</p>
<ul>
<li>mywebpack.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">const</span> fs = <span class="built_in">require</span>(<span class="string">"fs"</span>);</span><br><span class="line"><span class="keyword">const</span> babylon = <span class="built_in">require</span>(<span class="string">"babylon"</span>);</span><br><span class="line"><span class="keyword">const</span> traverse = <span class="built_in">require</span>(<span class="string">"babel-traverse"</span>).<span class="property">default</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">createAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> ast = babylon.<span class="title function_">parse</span>(content, {</span><br><span class="line"> <span class="attr">sourceType</span>: <span class="string">"module"</span>,</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="title function_">traverse</span>(ast, {</span><br><span class="line"> <span class="title class_">ImportDeclaration</span>: <span class="function">(<span class="params">{ node }</span>) =></span> {</span><br><span class="line"> <span class="variable language_">console</span>.<span class="title function_">log</span>(node);</span><br><span class="line"> },</span><br><span class="line"> });</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="title function_">createAsset</span>(<span class="string">"./source/entry.js"</span>);</span><br></pre></td></tr></table></figure>
<p><strong>6.获取 entry.js 的依赖</strong><br>可能会出现多个依赖，这里需要建一个数组存储。</p>
<ul>
<li>mywebpack.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">const</span> fs = <span class="built_in">require</span>(<span class="string">"fs"</span>);</span><br><span class="line"><span class="keyword">const</span> babylon = <span class="built_in">require</span>(<span class="string">"babylon"</span>);</span><br><span class="line"><span class="keyword">const</span> traverse = <span class="built_in">require</span>(<span class="string">"babel-traverse"</span>).<span class="property">default</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">createAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> ast = babylon.<span class="title function_">parse</span>(content, {</span><br><span class="line"> <span class="attr">sourceType</span>: <span class="string">"module"</span>,</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> dependencies = [];</span><br><span class="line"></span><br><span class="line"> <span class="title function_">traverse</span>(ast, {</span><br><span class="line"> <span class="title class_">ImportDeclaration</span>: <span class="function">(<span class="params">{ node }</span>) =></span> {</span><br><span class="line"> dependencies.<span class="title function_">push</span>(node.<span class="property">source</span>.<span class="property">value</span>);</span><br><span class="line"> },</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="variable language_">console</span>.<span class="title function_">log</span>(dependencies);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="title function_">createAsset</span>(<span class="string">"./source/entry.js"</span>);</span><br></pre></td></tr></table></figure>
<p>可以自行打印一下 dependencies 数组看看.这里输出的是一个包括 ImportDeclaration.source.value 的数组。</p>
<p><strong>7.优化 creatAsset 函数，增加 id 用于区分文件</strong></p>
<ul>
<li>mywebpack.js</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">const</span> fs = <span class="built_in">require</span>(<span class="string">"fs"</span>);</span><br><span class="line"><span class="keyword">const</span> babylon = <span class="built_in">require</span>(<span class="string">"babylon"</span>);</span><br><span class="line"><span class="keyword">const</span> traverse = <span class="built_in">require</span>(<span class="string">"babel-traverse"</span>).<span class="property">default</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">let</span> <span class="variable constant_">ID</span> = <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">createAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> ast = babylon.<span class="title function_">parse</span>(content, {</span><br><span class="line"> <span class="attr">sourceType</span>: <span class="string">"module"</span>,</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> dependencies = [];</span><br><span class="line"></span><br><span class="line"> <span class="title function_">traverse</span>(ast, {</span><br><span class="line"> <span class="title class_">ImportDeclaration</span>: <span class="function">(<span class="params">{ node }</span>) =></span> {</span><br><span class="line"> dependencies.<span class="title function_">push</span>(node.<span class="property">source</span>.<span class="property">value</span>);</span><br><span class="line"> },</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> id = <span class="variable constant_">ID</span>++;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> {</span><br><span class="line"> id,</span><br><span class="line"> filename,</span><br><span class="line"> dependencies,</span><br><span class="line"> };</span><br><span class="line">}</span><br><span class="line"><span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(<span class="string">"./source/entry.js"</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(mainAsset);</span><br></pre></td></tr></table></figure>
<p>运行一下看看, 是不是返回了正确的结果.</p>
<p><strong>8.现在我们有了单个文件的依赖了，接下来尝试建立模块间的依赖关系</strong><br>新建一个 createGraph 函数，在这个函数里引用 createAsset。<br>同时 entry 这个参数是动态的，所以 createGraph 接收 entry 这个参数。</p>
<ul>
<li>mywebpack.js - createGraph</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">createGraph</span>(<span class="params">entry</span>) {</span><br><span class="line"> <span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(entry);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">const</span> graph = <span class="title function_">createGraph</span>(<span class="string">"./source/entry.js"</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(graph);</span><br></pre></td></tr></table></figure>
<p>声明一个数组：allAsset 用于存储全部的 asset</p>
<ul>
<li>mywebpack.js - createGraph</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">createGraph</span>(<span class="params">entry</span>) {</span><br><span class="line"> <span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(entry);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">const</span> graph = <span class="title function_">createGraph</span>(<span class="string">"./source/entry.js"</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(graph);</span><br></pre></td></tr></table></figure>
<p><strong>9.把相对路径转换为绝对路径</strong><br>我们在 dependencies 中存储的都是相对路径，但是我们需要绝对路径才能拿到模块的 Asset，这个时候要想办法拿到每个模块的绝对路径。</p>
<blockquote>
<p>这里用到了 node 的另一个基础 API：path，其中用到了它的两个方法：<br>1.path.dirname(获取当前文件的路径名)<br>2.path.join(拼接路径)</p>
</blockquote>
<ul>
<li>mywebpack.js - createGraph</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">createGraph</span>(<span class="params">entry</span>) {</span><br><span class="line"> <span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(entry);</span><br><span class="line"> <span class="keyword">const</span> allAsset = [mainAsset];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">let</span> asset <span class="keyword">of</span> allAsset) {</span><br><span class="line"> <span class="keyword">const</span> dirname = path.<span class="title function_">dirname</span>(asset.<span class="property">filename</span>);</span><br><span class="line"> asset.<span class="property">dependencies</span>.<span class="title function_">forEach</span>(<span class="function">(<span class="params">relativePath</span>) =></span> {</span><br><span class="line"> <span class="keyword">const</span> absoultePath = path.<span class="title function_">join</span>(dirname, relativePath);</span><br><span class="line"> <span class="keyword">const</span> childAsset = <span class="title function_">createAsset</span>(absoultePath);</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>10.我们还需要一个 map,用于记录 dependencies 和 childAsset 之间的关系</strong><br>map 可以存储模块间的依赖关系，方便后续的查找。</p>
<ul>
<li>mywebpack.js - createGraph</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">createGraph</span>(<span class="params">entry</span>) {</span><br><span class="line"> <span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(entry);</span><br><span class="line"> <span class="keyword">const</span> allAsset = [mainAsset];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">let</span> asset <span class="keyword">of</span> allAsset) {</span><br><span class="line"> <span class="keyword">const</span> dirname = path.<span class="title function_">dirname</span>(asset.<span class="property">filename</span>);</span><br><span class="line"></span><br><span class="line"> asset.<span class="property">mapping</span> = {};</span><br><span class="line"></span><br><span class="line"> asset.<span class="property">dependencies</span>.<span class="title function_">forEach</span>(<span class="function">(<span class="params">relativePath</span>) =></span> {</span><br><span class="line"> <span class="keyword">const</span> absoultePath = path.<span class="title function_">join</span>(dirname, relativePath);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> childAsset = <span class="title function_">createAsset</span>(absoultePath);</span><br><span class="line"></span><br><span class="line"> asset.<span class="property">mapping</span>[relativePath] = childAsset.<span class="property">id</span>;</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>11.遍历所有文件，形成最终的依赖图 🌟🌟🌟🌟🌟</strong><br>核心的一步，就一行代码，完成所有模块的遍历。</p>
<ul>
<li>mywebpack.js - createGraph</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">createGraph</span>(<span class="params">entry</span>) {</span><br><span class="line"> <span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(entry);</span><br><span class="line"> <span class="keyword">const</span> allAsset = [mainAsset];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">let</span> asset <span class="keyword">of</span> allAsset) {</span><br><span class="line"> <span class="keyword">const</span> dirname = path.<span class="title function_">dirname</span>(asset.<span class="property">filename</span>);</span><br><span class="line"></span><br><span class="line"> asset.<span class="property">mapping</span> = {};</span><br><span class="line"></span><br><span class="line"> asset.<span class="property">dependencies</span>.<span class="title function_">forEach</span>(<span class="function">(<span class="params">relativePath</span>) =></span> {</span><br><span class="line"> <span class="keyword">const</span> absoultePath = path.<span class="title function_">join</span>(dirname, relativePath);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> childAsset = <span class="title function_">createAsset</span>(absoultePath);</span><br><span class="line"></span><br><span class="line"> asset.<span class="property">mapping</span>[relativePath] = childAsset.<span class="property">id</span>;</span><br><span class="line"> <span class="comment">//⬇️关键一步，向数组中推进子依赖</span></span><br><span class="line"> allAsset.<span class="title function_">push</span>(childAsset);</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> allAsset;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>获取到了文件依赖图之后，我们需要把所有文件打包成一个文件然后输出。</p>
<p><strong>12.新增一个方法 bundle</strong><br>最后一个函数了！胜利在望～<br>bundle 实现的是通过 graph 来创造一个立即执行函数，立即执行函数的参数有全部模块的代码体。</p>
<ul>
<li>mywebpack.js - bundle</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">bundle</span>(<span class="params">graph</span>) {</span><br><span class="line"> <span class="comment">//自执行函数的参数</span></span><br><span class="line"> <span class="keyword">let</span> modules = <span class="string">""</span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//遍历所有模块，拼接modules字符串：每个id对应一个value,value里要包括该module的可执行代码</span></span><br><span class="line"> graph.<span class="title function_">forEach</span>(<span class="function">(<span class="params"><span class="variable language_">module</span></span>) =></span> {</span><br><span class="line"> modules += <span class="string">`<span class="subst">${<span class="variable language_">module</span>.id}</span>:[</span></span><br><span class="line"><span class="string"></span></span><br><span class="line"><span class="string"> ],`</span>;</span><br><span class="line"> });</span><br><span class="line"> <span class="comment">//返回的结果</span></span><br><span class="line"> <span class="keyword">const</span> result = <span class="string">`</span></span><br><span class="line"><span class="string"> (function() {</span></span><br><span class="line"><span class="string"> </span></span><br><span class="line"><span class="string"> })({<span class="subst">${modules}</span>})</span></span><br><span class="line"><span class="string"> `</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>到现在我们会发现，graph 里只记录了每个模块对应的依赖关系，并没有包括可执行的代码体。<br>所以下一步，我们需要获取每个模块的代码体。</p>
<p>修改 createAsset 函数，获取到代码体且编译。</p>
<p>首先咱们会用到 babel-core,方便各个插件分析语法进行相应的处理。</p>
<p>安装他！<br><code>npm i babel-core</code></p>
<p>还会用到 babel-preset-env，它可以根据开发者的配置，按需加载插件，可以作为预设来编译代码。</p>
<p>安装他！<br><code>npm i babel-preset-env</code></p>
<ul>
<li>mywebpack.js - createAsset</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">createAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> ast = babylon.<span class="title function_">parse</span>(content, {</span><br><span class="line"> <span class="attr">sourceType</span>: <span class="string">"module"</span>,</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> dependencies = [];</span><br><span class="line"></span><br><span class="line"> <span class="title function_">traverse</span>(ast, {</span><br><span class="line"> <span class="title class_">ImportDeclaration</span>: <span class="function">(<span class="params">{ node }</span>) =></span> {</span><br><span class="line"> dependencies.<span class="title function_">push</span>(node.<span class="property">source</span>.<span class="property">value</span>);</span><br><span class="line"> },</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> id = <span class="variable constant_">ID</span>++;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> { code } = babel.<span class="title function_">transformFromAst</span>(ast, <span class="literal">null</span>, {</span><br><span class="line"> <span class="comment">// 第三个参数, 告诉babel以什么方式编译我们的代码. 这里我们就用官方提供的preset-env, 编译es2015+的js代码.</span></span><br><span class="line"> <span class="comment">// 当然还有其他的各种预设, 可以编译ts, react等等代码.</span></span><br><span class="line"> <span class="attr">presets</span>: [<span class="string">"env"</span>],</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> {</span><br><span class="line"> id,</span><br><span class="line"> filename,</span><br><span class="line"> dependencies,</span><br><span class="line"> code,</span><br><span class="line"> };</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>13.把获取到的 code 放到 result 中</strong><br>根据 commonJs 的规范，每个模块的代码函数需要接收三个参数：require,module,exports。</p>
<ul>
<li><p>module 变量代表当前的模块，它是一个变量，其中 exports 属性就是对外的模块。加载某个模块，其实就是加载该模块的 module.exports 属性。</p>
</li>
<li><p>mywebpack.js - bundle</p>
</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">bundle</span>(<span class="params">graph</span>) {</span><br><span class="line"> <span class="keyword">let</span> modules = <span class="string">""</span>;</span><br><span class="line"></span><br><span class="line"> graph.<span class="title function_">forEach</span>(<span class="function">(<span class="params"><span class="variable language_">module</span></span>) =></span> {</span><br><span class="line"> modules += <span class="string">`<span class="subst">${<span class="variable language_">module</span>.id}</span>:[</span></span><br><span class="line"><span class="string"> function(require, module, exports) {</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="variable language_">module</span>.code}</span></span></span><br><span class="line"><span class="string"> },</span></span><br><span class="line"><span class="string"> ],`</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> result = <span class="string">`</span></span><br><span class="line"><span class="string"> (function() {</span></span><br><span class="line"><span class="string"> </span></span><br><span class="line"><span class="string"> })({<span class="subst">${modules}</span>})</span></span><br><span class="line"><span class="string"> `</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>接下来开始实现 require 函数，首先需要把 mapping 传到对应 modules 的 value 里面。</p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">bundle</span>(<span class="params">graph</span>) {</span><br><span class="line"> <span class="keyword">let</span> modules = <span class="string">""</span>;</span><br><span class="line"></span><br><span class="line"> graph.<span class="title function_">forEach</span>(<span class="function">(<span class="params"><span class="variable language_">module</span></span>) =></span> {</span><br><span class="line"> modules += <span class="string">`<span class="subst">${<span class="variable language_">module</span>.id}</span>:[</span></span><br><span class="line"><span class="string"> function(require, module, exports) {</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="variable language_">module</span>.code}</span></span></span><br><span class="line"><span class="string"> },</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="built_in">JSON</span>.stringify(<span class="variable language_">module</span>.mapping)}</span>,</span></span><br><span class="line"><span class="string"> ],`</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> result = <span class="string">`</span></span><br><span class="line"><span class="string"> (function() {</span></span><br><span class="line"><span class="string"> </span></span><br><span class="line"><span class="string"> })({<span class="subst">${modules}</span>})</span></span><br><span class="line"><span class="string"> `</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>requier 要接收一个参数，来表示引入了哪些代码，这个时候就可以用 mapping 的映射关系，使用 id 找到引入的代码。</p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">function</span> <span class="title function_">bundle</span>(<span class="params">graph</span>) {</span><br><span class="line"> <span class="keyword">let</span> modules = <span class="string">""</span>;</span><br><span class="line"></span><br><span class="line"> graph.<span class="title function_">forEach</span>(<span class="function">(<span class="params"><span class="variable language_">module</span></span>) =></span> {</span><br><span class="line"> modules += <span class="string">`<span class="subst">${<span class="variable language_">module</span>.id}</span>:[</span></span><br><span class="line"><span class="string"> function(require, module, exports) {</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="variable language_">module</span>.code}</span></span></span><br><span class="line"><span class="string"> },</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="built_in">JSON</span>.stringify(<span class="variable language_">module</span>.mapping)}</span>,</span></span><br><span class="line"><span class="string"> ],`</span>;</span><br><span class="line"> });</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 取出的fn是上面定义的modules里的function，mapping是${JSON.stringify(module.mapping)}</span></span><br><span class="line"> <span class="keyword">const</span> result = <span class="string">`</span></span><br><span class="line"><span class="string"> (function(modules) {</span></span><br><span class="line"><span class="string"> function require(id) {</span></span><br><span class="line"><span class="string"> const [fn, mapping] = modules[id];</span></span><br><span class="line"><span class="string"></span></span><br><span class="line"><span class="string"> function localRequire(relativePath) {</span></span><br><span class="line"><span class="string"> return require(mapping[relativePath]);</span></span><br><span class="line"><span class="string"> }</span></span><br><span class="line"><span class="string"></span></span><br><span class="line"><span class="string"> const module = { exports: {}};</span></span><br><span class="line"><span class="string"></span></span><br><span class="line"><span class="string"> fn(localRequire, module, module.exports);</span></span><br><span class="line"><span class="string"></span></span><br><span class="line"><span class="string"> return module.exports;</span></span><br><span class="line"><span class="string"> }</span></span><br><span class="line"><span class="string"> require(0);</span></span><br><span class="line"><span class="string"> })({<span class="subst">${modules}</span>})</span></span><br><span class="line"><span class="string"> `</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>当当当！到这里就基本完成了我们的简易版 webpack,这个时候可以 node 运行下 mywebpack.js，把输出的结果代码复制到浏览器里看看能不能正常运行。<br>浏览器打印出：Yolanda is a girl 就意味着你的 webpack 已经正常运转起来了！给自己鼓个掌吧～</p>
<p>最后可以优化一下流程，每次都复制到浏览器看输出结果有点费劲，可以配置下 package.json 用命令行操作。<br><code>npm init</code></p>
<ul>
<li>package.json</li>
</ul>
<figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">"scripts"</span><span class="punctuation">:</span> <span class="punctuation">{</span></span><br><span class="line"> <span class="attr">"build"</span><span class="punctuation">:</span> <span class="string">"rm -rf dist.js && node mywebpack.js > dist.js"</span></span><br><span class="line"><span class="punctuation">}</span><span class="punctuation">,</span></span><br></pre></td></tr></table></figure>
<p>最后运行</p>
<p><code>npm run build</code>.</p>
<p>大功告成！</p>
<h2 id="贴上-mywebpack-js-完整代码："><a href="#贴上-mywebpack-js-完整代码：" class="headerlink" title="贴上 mywebpack.js 完整代码："></a>贴上 mywebpack.js 完整代码：</h2><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 步骤：</span></span><br><span class="line"><span class="comment">// 1.找到一个入口文件；</span></span><br><span class="line"><span class="comment">// 2.解析这个入口文件，提起入口文件的依赖；</span></span><br><span class="line"><span class="comment">// 3.解析入口文件中依赖的依赖，递归的创造一个依赖图，可以描述文件间的依赖关系；</span></span><br><span class="line"><span class="comment">// 4.将所有的文件打包成一个文件。</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//node里面的fs模块可以读取文件</span></span><br><span class="line"><span class="keyword">const</span> fs = <span class="built_in">require</span>(<span class="string">"fs"</span>);</span><br><span class="line"><span class="comment">//node的基础api 可以帮助拿到绝对路径</span></span><br><span class="line"><span class="keyword">const</span> path = <span class="built_in">require</span>(<span class="string">"path"</span>);</span><br><span class="line"><span class="comment">//babel（语法转换）的解析工具</span></span><br><span class="line"><span class="keyword">const</span> babylon = <span class="built_in">require</span>(<span class="string">"babylon"</span>);</span><br><span class="line"><span class="comment">//babel-traverse :可以像遍历对象一样遍历ast中的节点</span></span><br><span class="line"><span class="keyword">const</span> tranverse = <span class="built_in">require</span>(<span class="string">"babel-traverse"</span>).<span class="property">default</span>;</span><br><span class="line"><span class="comment">//babel-core:把js文件解析为ast</span></span><br><span class="line"><span class="keyword">const</span> babel = <span class="built_in">require</span>(<span class="string">"babel-core"</span>);</span><br><span class="line"></span><br><span class="line"><span class="comment">//记录ID</span></span><br><span class="line"><span class="keyword">let</span> <span class="variable constant_">ID</span> = <span class="number">0</span>;</span><br><span class="line"><span class="comment">//拿到该file的id，filename 以及 依赖的数组</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">createAsset</span>(<span class="params">filename</span>) {</span><br><span class="line"> <span class="comment">//同步的读取文件</span></span><br><span class="line"> <span class="keyword">const</span> content = fs.<span class="title function_">readFileSync</span>(filename, <span class="string">"utf-8"</span>);</span><br><span class="line"> <span class="comment">//转化为ast找到相应节点</span></span><br><span class="line"> <span class="keyword">const</span> ast = babylon.<span class="title function_">parse</span>(content, {</span><br><span class="line"> <span class="attr">sourceType</span>: <span class="string">"module"</span>,</span><br><span class="line"> });</span><br><span class="line"> <span class="comment">//定义一个数组用于储存依赖</span></span><br><span class="line"> <span class="keyword">const</span> dependencies = [];</span><br><span class="line"> <span class="comment">//定义一个id 每调用一次creatAsset函数id++</span></span><br><span class="line"> <span class="keyword">let</span> id = <span class="variable constant_">ID</span>++;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//遍历拿到ImportDeclaration中的source中的value</span></span><br><span class="line"> <span class="title function_">tranverse</span>(ast, {</span><br><span class="line"> <span class="title class_">ImportDeclaration</span>: <span class="function">(<span class="params">{ node }</span>) =></span> {</span><br><span class="line"> <span class="comment">//拿到node中的source的value push到储存依赖的数组里</span></span><br><span class="line"> dependencies.<span class="title function_">push</span>(node.<span class="property">source</span>.<span class="property">value</span>);</span><br><span class="line"> },</span><br><span class="line"> });</span><br><span class="line"> <span class="keyword">const</span> { code } = babel.<span class="title function_">transformFromAst</span>(ast, <span class="literal">null</span>, {</span><br><span class="line"> <span class="attr">presets</span>: [<span class="string">"env"</span>],</span><br><span class="line"> });</span><br><span class="line"> <span class="comment">//输出一个对象，其中包括id，filename以及它所依赖的dependencies</span></span><br><span class="line"> <span class="keyword">return</span> {</span><br><span class="line"> id,</span><br><span class="line"> filename,</span><br><span class="line"> dependencies,</span><br><span class="line"> code,</span><br><span class="line"> };</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//创建依赖图 核心！！</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">createGraph</span>(<span class="params">entry</span>) {</span><br><span class="line"> <span class="keyword">const</span> mainAsset = <span class="title function_">createAsset</span>(entry);</span><br><span class="line"> <span class="keyword">const</span> allAsset = [mainAsset];</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">let</span> asset <span class="keyword">of</span> allAsset) {</span><br><span class="line"> <span class="comment">//拿到当前的dirname</span></span><br><span class="line"> <span class="keyword">const</span> dirname = path.<span class="title function_">dirname</span>(asset.<span class="property">filename</span>);</span><br><span class="line"> <span class="comment">//给asset新增一个mapping对象，方便后续查找</span></span><br><span class="line"> asset.<span class="property">mapping</span> = {};</span><br><span class="line"> <span class="comment">//将dependencies中的相对路径转化为绝对路径</span></span><br><span class="line"> asset.<span class="property">dependencies</span>.<span class="title function_">forEach</span>(<span class="function">(<span class="params">relativePath</span>) =></span> {</span><br><span class="line"> <span class="keyword">const</span> absolutePath = path.<span class="title function_">join</span>(dirname, relativePath);</span><br><span class="line"> <span class="comment">//拿到绝对路径下的子元素的asset内容</span></span><br><span class="line"> <span class="keyword">const</span> childAsset = <span class="title function_">createAsset</span>(absolutePath);</span><br><span class="line"> <span class="comment">//存储对应关系</span></span><br><span class="line"> asset.<span class="property">mapping</span>[relativePath] = childAsset.<span class="property">id</span>;</span><br><span class="line"> <span class="comment">//递归的核心一行代码！！🌟🌟🌟🌟🌟</span></span><br><span class="line"> allAsset.<span class="title function_">push</span>(childAsset);</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> allAsset;</span><br><span class="line">}</span><br><span class="line"><span class="comment">//创建整体结果代码块（需要立即执行）接收module作为参数</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">bundle</span>(<span class="params">graph</span>) {</span><br><span class="line"> <span class="keyword">let</span> modules = <span class="string">""</span>;</span><br><span class="line"> graph.<span class="title function_">forEach</span>(<span class="function">(<span class="params"><span class="variable language_">module</span></span>) =></span> {</span><br><span class="line"> modules += <span class="string">`</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="variable language_">module</span>.id}</span>:[</span></span><br><span class="line"><span class="string"> function(require,module,exports){</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="variable language_">module</span>.code}</span></span></span><br><span class="line"><span class="string"> },</span></span><br><span class="line"><span class="string"> <span class="subst">${<span class="built_in">JSON</span>.stringify(<span class="variable language_">module</span>.mapping)}</span></span></span><br><span class="line"><span class="string"> ],</span></span><br><span class="line"><span class="string"> `</span>;</span><br><span class="line"> });</span><br><span class="line"> <span class="comment">//输出的结果为字符串</span></span><br><span class="line"> <span class="keyword">const</span> result = <span class="string">`(</span></span><br><span class="line"><span class="string"> function(modules){</span></span><br><span class="line"><span class="string"> function require(id){</span></span><br><span class="line"><span class="string"> const [fn,mapping] = modules[id];</span></span><br><span class="line"><span class="string"> function localRequire(relativePath){</span></span><br><span class="line"><span class="string"> return require(mapping[relativePath])</span></span><br><span class="line"><span class="string"> }</span></span><br><span class="line"><span class="string"> const module = { exports:{}}</span></span><br><span class="line"><span class="string"> fn(localRequire,module,module.exports)</span></span><br><span class="line"><span class="string"> </span></span><br><span class="line"><span class="string"> return module.exports</span></span><br><span class="line"><span class="string"> }</span></span><br><span class="line"><span class="string"> require(0)</span></span><br><span class="line"><span class="string"> }</span></span><br><span class="line"><span class="string"> )({<span class="subst">${modules}</span>})`</span>;</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//传入相对路径</span></span><br><span class="line"><span class="keyword">const</span> graph = <span class="title function_">createGraph</span>(<span class="string">"./source/entry.js"</span>);</span><br><span class="line"><span class="keyword">const</span> res = <span class="title function_">bundle</span>(graph);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(res);</span><br></pre></td></tr></table></figure>
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