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I'm reading Ionic's source code. I came across this regex, and i"m pretty baffled by it.
([\s\S]+?)
Ok, it's grouping on every char that is either a white space, or non white space???
Why didn't they just do
(.+?)
Am I missing something?
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* means zero-or-more, and + means one-or-more. So the difference is that the empty string would match the second expression but not the first.
Note that a* means zero or more occurrence of a in the string while a+ means that one or more occurrence of a in the string. That means a* denotes language L = {є , a, aa, aaa, ….}
is called the wildcard character. Example : The Regular expression . * will tell the computer that any character can be used any number of times. Optional character – ( ? )
(. *?) matches any character ( . ) any number of times ( * ), as few times as possible to make the regex match ( ? ). You'll get a match on any string, but you'll only capture a blank string because of the question mark.
The . matches any symbol but a newline. In order to make it match a newline, in most languages there is a modifier (dotall, singleline). However, in JS, there is no such a modifier.
Thus, a work-around is to use a [\s\S] character class that will match any character, including a newline, because \s will match all whitespace and \S will match all non-whitespace characters. Similarly, one could use [\d\D] or [\w\W].
Also, there is a [^] pattern to match the same thing in JS, but since it is JavaScript-specific, the regexes containing this pattern are not portable between regex flavors.
The +? lazy quanitifier matches 1 or more symbols conforming to the preceding subpattern, but as few as possible. Thus, it will match just 1 symbol if used like this, at the end of the pattern.
73
In many realizations of Regexp "." doesn't match new lines. So they use "[\s\S]" as a little hack =)
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