Html url/src/href 属性中的两个正斜杠
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Two forward slashes in a url/src/href attribute
提问by Michael Parkin
Possible Duplicate:
URI starting with two slashes … how do they behave?
Absolute URLs omitting the protocol (scheme) in order to preserve the one of the current page
shorthand as // for script and link tags? anyone see / use this before?
可能的重复：
URI 以两个斜杠开头……它们的行为如何？
为了将当前页面速记之一保留为 // 用于脚本和链接标签，绝对 URL 省略了协议（方案）
？有人看过/使用过吗？
I was looking through the source of HTML5 Resetwhen I noticed the following line:
当我注意到以下行时，我正在查看HTML5 Reset的源代码：
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
Why does the URL start with two forward slashes? Is this a shorthand for http://?
为什么 URL 以两个正斜杠开头？这是 的简写http://吗？
回答by vzwick
The "two forward slashes" are a common shorthand for "whatever protocol is being used right now".
“两个正斜杠”是“现在正在使用的任何协议”的常见简写。
Best known as "protocol relative URLs", they are particularly useful when elements — such as the JS file in your example — could be loaded from either a httpor a httpscontext. By using protocol relative URLs, you can avoid implementing
最著名的是“协议相对 URL”，当元素（例如示例中的 JS 文件）可以从 ahttp或https上下文加载时，它们特别有用。通过使用协议相对 URL，您可以避免实现
if (window.location.protocol === 'http:') {
myResourceUrl = 'http://example.com/my-resource.js';
} else {
myResourceUrl = 'https://example.com/my-resource.js';
}
type of logic all over your codebase (assuming, of course, that the server at example.comis able to serve resources via both httpand https).
整个代码库中的逻辑类型（当然，假设服务器 atexample.com能够通过http和提供资源https）。
A prominent real-world example is the Magento E-Commerce engine: for performance reasons, the shop's pages use plain httpby default, whereas the checkout is httpsenabled.
一个突出的现实世界的例子是 Magento 电子商务引擎：出于性能原因，商店的页面http默认使用普通的，而结账是https启用的。
When hard-coded resources (i.e. promotional banners in the site's header) are referenced by non protocol relative URLs (i.e. http://example.com/banner.jpg), customers reaching the httpsenabled checkout will be greeted with a rather unfriendly
当硬编码资源（即站点标题中的促销横幅）被非协议相对 URL（即http://example.com/banner.jpg）引用时，到达https启用结帐的客户将受到相当不友好的欢迎
"there are insecure elements on this page"
“此页面上存在不安全元素”
prompt - which, as you can imagine, throws the average non-tech-savvy person off.
提示 - 正如您可以想象的那样，这会让普通的非精通技术的人望而却步。
If the aforementioned resource is referenced via //example.com/banner.jpgthough, the browser takes care of prepending the proper protocol.
如果通过//example.com/banner.jpg尽管引用上述资源，浏览器会负责预先准备正确的协议。
tl;dr: With even the slightest possibility of a mixed http/https environment, just use the double slash/protocol relative URLs for loading your resources — assuming that the host serving the content is both http and https enabled.
tl;dr：即使是最轻微的混合 http/https 环境的可能性，也只需使用双斜杠/协议相对 URL 来加载您的资源——假设提供内容的主机同时启用了 http 和 https。
回答by Radu Cugut
It will automatically add https or http, depending on how the request was made.
它会自动添加 https 或 http，具体取决于请求的方式。
