In-depth understanding of the analysis of quantifiers in JS regular expressions-JS Tutorial-php.cn

Quantifiers

This article mainly introduces the analysis of quantifiers for in-depth understanding of JS regular expressions. It has a certain reference value. Now I share it with you. Friends in need can refer to it

Many times, we need to match a string with characters that appear many times in a row. For example, we need to match a string with a number that appears 20 times in a row. According to the previous writing:

\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d

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Does it feel fast? crazy? Fortunately, using the quantifiers provided by regular expressions, we can quickly solve this problem. The usage of

quantifiers is as follows:

Characters	Meaning
?	Occurs zero or once (occurs at most once)
	Occurs one or more times (occurs at least once)
*	Occurs zero or more times (any number of times)
{n}	Occurs n times
{n,m}	occurs n to m times
{n,}	Occurs at least n times

#So how to use quantifiers to solve the previous problem?

It's very simple, just need:

\d{20}

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What should you do if you want to match up to n times? Many people will want to imitate it appearing at least n times and write it as{,n}, but the regular expression will directly treat it as an ordinary string. Only by writing it as{0, n}can match at most n times.

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