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class="container" id="main-content" tabindex="-1"><div class="post"><article class="post-block h-entry"><div class="post-meta p-author h-card visually-hidden"><img class="author-avatar u-photo" src="../favicon.png" alt="Cytrogen"><span class="p-name">Cytrogen</span><a class="u-url" href="https://cytrogen.icu">https://cytrogen.icu</a></div><a class="post-permalink u-url u-uid visually-hidden" href="https://cytrogen.icu/posts/e6b8.html">永久链接</a><div class="visually-hidden"><a class="p-category" href="../categories/%E7%BC%96%E7%A8%8B%E7%AC%94%E8%AE%B0/">编程笔记</a></div><h1 class="post-title p-name">NestJS 里开发 MJML 模板邮件</h1><div class="post-info"><time class="post-date dt-published" datetime="2025-12-10T16:18:10.000Z">12/10/2025</time><time class="dt-updated visually-hidden" datetime="2026-02-09T17:16:54.733Z"></time></div><div class="post-content e-content"><html><head></head><body><p>工作要求，需要在项目里写 MJML 模板邮件。差不多就是在服务端内写好所有的邮件模板，到时候发送的时候选哪个发送哪个。</p>
<p>在 NestJS 框架下写模板邮件有这些问题：</p>
<ol>
<li>如何让框架知道哪些模板文件存在？</li>
<li>如何检查 MJML 语法？</li>
<li>如何验证占位符是否存在？</li>
<li>如何看到真实邮件内容差异？</li>
<li>如何让程序检查每个占位符是否正确？</li>
</ol>
<h2 id="mjml-变量类型验证"><a class="markdownIt-Anchor" href="#mjml-变量类型验证"></a> MJML 变量类型验证</h2>
<p>我的方案是，写一个 service 可以自动提取 MJML 模板里的变量，然后与一个手动写好的 TypeScript 类型定义进行对比验证。</p>
<p>提取逻辑很简单，用正则就好。</p>
<p>麻烦一点的是模板类型定义，需要自己手动写。</p>
<p>我会建议这么做：</p>
<ol>
<li>定义邮件系统中所有可能用到的每一个占位符，并且强制规定命名规范</li>
<li>为每一个字段都定义一个数据类型、是否必需以及描述</li>
<li>将这些占位符组合成多个可复用的模板组，例如 footer 模板组</li>
<li>写一个检查器，要可以检查所有的 MJML 占位符、根据提取出来的变量与已经定位好的占位符进行比对，然后指出问题所在</li>
</ol>
<p>这么做之后，就可以在发出有问题的邮件之前报错。</p>
<h2 id="mjml-lint-工具"><a class="markdownIt-Anchor" href="#mjml-lint-工具"></a> MJML Lint 工具</h2>
<p>Lint 真的很好用，所以我想要在 MJML 里也写这么一个 Lint 工具。</p>
<h3 id="mjml-热加载"><a class="markdownIt-Anchor" href="#mjml-热加载"></a> MJML 热加载</h3>
<p>我遇到了一个坑。</p>
<p>我使用了 chokidar 来监听文件系统变化。</p>
<p>结果问题在于，chokidar 在 Node.JS 进程启动时进行初始化时，容易出错并且导致 Node.JS 进程直接崩溃。</p>
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