我正在尝试使用从http://daringfireball.net/2010/07/improved_regex_for_matching_urls获取的URL匹配正则表达式。
(?xi)
\b
( # Capture 1: entire matched URL
(?:
https?:// # http or https protocol
| # or
www\d{0,3}[.] # "www.", "www1.", "www2." … "www999."
| # or
[a-z0-9.\-]+[.][a-z]{2,4}/ # looks like domain name followed by a slash
)
(?: # One or more:
[^\s()<>]+ # Run of non-space, non-()<>
| # or
\(([^\s()<>]+|(\([^\s()<>]+\)))*\) # balanced parens, up to 2 levels
)+
(?: # End with:
\(([^\s()<>]+|(\([^\s()<>]+\)))*\) # balanced parens, up to 2 levels
| # or
[^\s`!()\[\]{};:'".,<>?«»“”‘’] # not a space or one of these punct chars
)
)
根据另一个问题的答案,似乎有些情况会导致这个正则表达式出现灾难性回溯。例如:
var re = /\b((?:https?:\/\/|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))/i;
re.test("http://google.com/?q=(AAAAAAAAAAAAAAAAAAAAAAAAAAAAA)")
...执行起来可能需要很长时间(例如在Chrome中)
我认为问题出在代码的这部分:
(?: # One or more:
[^\s()<>]+ # Run of non-space, non-()<>
| # or
\(([^\s()<>]+|(\([^\s()<>]+\)))*\) # balanced parens, up to 2 levels
)+
...这似乎大致相当于(.+|\((.+|(\(.+\)))*\))+
,其中包含(.+)+
有没有我可以做出的更改来避免这种情况?