url/src/href 属性中的两个正斜杠 [英] Two forward slashes in a url/src/href attribute

问题描述

可能的重复:
URI 以两个斜线开头 …他们的行为如何?
绝对网址省略协议(方案)以保留当前页面之一
简写为//脚本和链接标签?有人看过/使用过吗?

当我注意到 HTML5 Resethttps://github.com/murtaugh/HTML5-Reset/blob/master/index.html#L113" rel="noreferrer">以下行:

I was looking through the source of HTML5 Reset when I noticed the following line:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>

为什么 URL 以两个正斜杠开头?这是 http:// 的简写吗?

Why does the URL start with two forward slashes? Is this a shorthand for http://?

推荐答案

两个正斜杠"是现在正在使用的任何协议"的常用简写.

最广为人知的协议相对 URL"，当元素(例如示例中的 JS 文件)可以从 http 或 https<加载时，它们特别有用./代码> 上下文.通过使用协议相对 URL，您可以避免实现

The "two forward slashes" are a common shorthand for "whatever protocol is being used right now".

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 http or a https context. By using protocol relative URLs, you can avoid implementing

if (window.location.protocol === 'http:') {
    myResourceUrl = 'http://example.com/my-resource.js';
} else {
    myResourceUrl = 'https://example.com/my-resource.js';
}

整个代码库中的逻辑类型(当然，假设 example.com 上的服务器能够通过 http 和 https).

type of logic all over your codebase (assuming, of course, that the server at example.com is able to serve resources via both http and https).

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，商店的页面默认使用纯 http，而结账是启用 https.

A prominent real-world example is the Magento E-Commerce engine: for performance reasons, the shop's pages use plain http by default, whereas the checkout is https enabled.

当硬编码资源(即网站标题中的促销横幅)被非协议相对 URL(即 http://example.com/banner.jpg)引用时，客户到达 https 启用的结帐将受到相当不友好的欢迎

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 https enabled checkout will be greeted with a rather unfriendly

此页面上存在不安全元素"

"there are insecure elements on this page"

提示 - 正如您想象的那样，这会让一般不精通技术的人望而却步.

prompt - which, as you can imagine, throws the average non-tech-savvy person off.

如果上述资源是通过 //example.com/banner.jpg 引用的，浏览器会负责预先准备正确的协议.

If the aforementioned resource is referenced via //example.com/banner.jpg though, the browser takes care of prepending the proper protocol.

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.

这篇关于url/src/href 属性中的两个正斜杠的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！