问题描述
我希望用户提交一个有效但也是图像的 URL，以 .jpg、.png 或 .gif 结尾.
I would like users to submit a URL that is valid but also is an image, ending with .jpg, .png, or .gif.
推荐答案
(?:([^:/?#]+):)?(?://([^/?#]*))?([^?#]*.(?:jpg|gif|png))(?:?([^#]*))?(?:#(.*))?这是来自 RFC 2396 的官方 URI 解析正则表达式的(稍微修改)版本.它允许 #fragments 和 ?querystrings 出现在文件名之后，这可能是也可能不是你想要的.它还匹配任何有效的域，包括 localhost，这也可能不是您想要的，但可以修改.
That's a (slightly modified) version of the official URI parsing regexp from RFC 2396. It allows for #fragments and ?querystrings to appear after the filename, which may or may not be what you want. It also matches any valid domain, including localhost, which again might not be what you want, but it could be modified.
更传统的正则表达式可能如下所示.
A more traditional regexp for this might look like the below.
^https?://(?:[a-z0-9-]+.)+[a-z]{2,6}(?:/[^/#?]+)+.(?:jpg|gif|png)$
|-------- domain -----------|--- path ---|-- extension ---|编辑见我的其他评论，虽然没有像这个评论那样完整地回答问题，但我觉得在这种情况下它可能更有用.但是，出于 完整性原因，我将其留在这里.
EDIT See my other comment, which although isn't answering the question as completely as this one, I feel it's probably a more useful in this case. However, I'm leaving this here for completeness reasons.
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