June 2021
Intermediate to advanced
290 pages
9h 21m
Chinese
Content preview from Node与Express开发（第2版）
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静态内容
｜
189
17.2
内容分发网络
（
CDN
）
当你要把网站推上生产的时候，网站的静态资源必须存放于互联网上的
某个地方
。你也许
习惯于把它们存放在生成所有动态
HTML
的同一台服务器上
，目前为止我们的示例应用也
是这么做的：使用
node meadowlark.js
运行起来的
Node/Express
服务器，除了提供
HTML
服务之外，还提供静态资源服务。不过，如果你想最大化网站的性能（或者希望在将来能
够做到），就会希望把静态资源托管到一个
CDN
上。
CDN
就是把分发静态资源优化到极
致的服务器。它通过专门的响应头（一会儿就会学习）启用了浏览器缓存。
CDN
也可以启用
基于地理位置的优化
（常称为
边缘缓存
），也就是说，
CDN
可以先找出地
理上距当前客户端最近的一台服务器，然后从这台服务器发送静态内容。虽然互联网传输
数据很快（虽不是以光速运行，但也很接近），但是传输
100
英里还是比
1000
英里速度要
快。虽然单次节省的时间或许很少，但如果考虑到用户数、请求数、资源数，累积起来就
显得快了。
大多数静态资源是在
HTML
视图中引用的
（通过
<link>
标签引用
CSS
文件、
<script>
引用
JavaScript
文件、
<img>
引用图片文件，再加上多媒体嵌入标签）。
CSS
文件中包
含静态引用也是很常见的，比如通常使用的
background-image
属性。最后，有时候在
JavaScript
中也会引用静态资源
，比如有的
JavaScript
代码会动态地修改或插入
<img>
标签
或
background-image
属性。
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.