正则表达式解释

发布于 2024-08-09 19:35:21 字数 200 浏览 7 评论 0原文

我正在查看 tumblr 书签中的代码，很好奇下面的代码做了什么。

try{
    if(!/^(.*\.)?tumblr[^.]*$/.test(l.host))
        throw(0);
        tstbklt();
}

谁能告诉我 if 线正在测试什么？我尝试解码正则表达式但无法做到这一点。

原文

I am looking at the code in the tumblr bookmarklet and was curious what the code below did.

try{
    if(!/^(.*\.)?tumblr[^.]*$/.test(l.host))
        throw(0);
        tstbklt();
}

Can anyone tell me what the if line is testing? I have tried to decode the regex but have been unable to do so.

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情绪 2024-08-16 19:35:21

最初排除正则表达式的细节，此代码为：

if ( ! /.../.test(l.host) )

“if not regex.matches(l.host)”或“if l.host does not match this regex”

因此，正则表达式必须正确描述 l.host 文本的内容使条件失败，从而避免抛出错误。

关于正则表达式本身：

^(.*\.)?tumblr[^.]*$

这是检查 tumblr 是否存在，但仅在可能存在的以 . 结尾的任何字符串之后：

^       # start of line
(       # begin capturing group 1
.*      # match any (non-newline) character, as many times as possible, but zero allowed
\.      # match a literal .
)       # end capturing group 1
?       # make whole preceeding item optional
tumblr  # match literal text tumblr
[^.]*   # match any non . character, as many times as possible, but zero allowed
$       # match end of line

我以为是在测试主机是否是tumblr

，看起来可能是为了检查这一点，但如果是这样，那就是错误的做法。
为此，第一位应该类似于 ^(?:[\w-]+\.)? 来捕获字母数字子域（?: 是一个非-捕获组，[\w-]+ 至少为 1 个字母数字、下划线或连字符），最后一位应为 \.(?:com|net|org)$ 或者类似于 (?:\.[a-zA-Z]+)+$ ，具体取决于 tld 部分可能需要的灵活性。

Initially excluding the specifics of the regex, this code is:

if ( ! /.../.test(l.host) )

"if not regex.matches(l.host)" or "if l.host does not match this regex"

So, the regex must correctly describe the contents of l.host text for the conditional to fail and thus avoid throwing the error.

On to the regex itself:

^(.*\.)?tumblr[^.]*$

This is checking for the existence of tumblr but only after any string ending in . that might exist:

^       # start of line
(       # begin capturing group 1
.*      # match any (non-newline) character, as many times as possible, but zero allowed
\.      # match a literal .
)       # end capturing group 1
?       # make whole preceeding item optional
tumblr  # match literal text tumblr
[^.]*   # match any non . character, as many times as possible, but zero allowed
$       # match end of line

I thought it was testing to see if the host was tumblr

Yeah, it looked like it might be intended to check that, but if so it's the wrong way to do it.
For that, the first bit should be something like ^(?:[\w-]+\.)? to capture an alphanumeric subdomain (the ?: is a non-capturing group, the [\w-]+ is at least 1 alphanumeric, underscore or hyphen) and the last bit should be either \.(?:com|net|org)$ or perhaps like (?:\.[a-zA-Z]+)+$ depending on how flexible the tld section might need to be.

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