regex

tony2099 included in regex

2021-01-15 182 words One minute

Contents

match. a type:

\d: number
\w: [a-z] [0-9_]
\s: any whitespace
.: match any charcter., except for \n

match times:

?: [0,1]
+:[1, +unlimited]
- : [0, +unlimited]

2. syntax

base

single char	quantifiers(数量)	position(位置)
\d 匹配数字	* 0个或者更多	^一行的开头
\w 匹配word(数字、字母)	+ 1个或更多，至少1个	$一行的结尾
\W 匹配非word(数字、字母)	? 0个或1个,一个Optional	\b 单词"结界"(word bounds)
\s 匹配white space(包括空格、tab等)	{min,max}出现次数在一个范围内
\S 匹配非white space(包括空格、tab等)	{n}匹配出现n次的
. 匹配任何，任何的字符

1. character class(character set)

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The lynk is quite a link don't you think? l nk l(nk

正则表达式： l[yi (]nk

结果:

1

lynk  link  l nk   l(nk

match mode

[Specifying Modes Inside The Regular Expression(https://www.regular-expressions.info/modifiers.html)

Flag Meaning i case-insensitive m let ^ and $ match begin/end line in addition to begin/end text (multi-line mode) s let . match \n (single-line mode)

(?i): case insensitive (?g): global

Normally, matching modes are specified outside the regular expression.

/abc/i

如果语言不支持，可以这么定义

(?i)abc

greedy mode vs lazy mode

greedy mode: + or .

lazy mode: put ? after + or .

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let regexp = /".+?"/g;

let str = 'a "witch" and her "broom" is one';

alert( str.match(regexp) ); // witch, broom