html - URI 以两个斜杠开头……它们的行为如何？

Question

最近我看到了像这样的工作代码块:

<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>

并且根据 RFC 2396(URI 语法)和 RFC 2616(HTTP 1.1)，这些以两个斜杠开头的 URI 是有效的，但不幸的是 RFC 并没有真正解释它们。

任何人都可以向我指出解释浏览器将/应该/确实如何处理这些 URI 的资源吗？

Answer 1

您正在寻找的资源是 RFC 3986 .

参见第 4.2 节和第 5.4 节。引用后者:

Reference Resolution Examples

Within a representation with a well defined base URI of:

    http://a/b/c/d;p?q

a relative reference is transformed to its target URI as follows:

  "g:h"           =  "g:h"
  "g"             =  "http://a/b/c/g"
  "./g"           =  "http://a/b/c/g"
  "g/"            =  "http://a/b/c/g/"
  "/g"            =  "http://a/g"
  "//g"           =  "http://g"
  "?y"            =  "http://a/b/c/d;p?y"
  "g?y"           =  "http://a/b/c/g?y"
  "#s"            =  "http://a/b/c/d;p?q#s"
  "g#s"           =  "http://a/b/c/g#s"
  "g?y#s"         =  "http://a/b/c/g?y#s"
  ";x"            =  "http://a/b/c/;x"
  "g;x"           =  "http://a/b/c/g;x"
  "g;x?y#s"       =  "http://a/b/c/g;x?y#s"
  ""              =  "http://a/b/c/d;p?q"
  "."             =  "http://a/b/c/"
  "./"            =  "http://a/b/c/"
  ".."            =  "http://a/b/"
  "../"           =  "http://a/b/"
  "../g"          =  "http://a/b/g"
  "../.."         =  "http://a/"
  "../../"        =  "http://a/"
  "../../g"       =  "http://a/g"

这意味着当基础 URI 是 http://a/b/c/d;p?q 而你使用 //g 时，相对引用转换为 http://g。