正则表达式的基本使用
推荐正则测试网站: https://regexr.com/ (opens new window)
# 1. 基本匹配
'name' => my name is Paul.
'Paul' => my name is Paul.
# 2. 元字符匹配
| 字符 | 描述 |
|---|---|
| . | 匹配任意单个字符,换行符除外 |
| [] | 匹配方括号之间任意字符 |
| [^] | 否定字符类。匹配方括号之间不包含的任何字符 |
| * | 匹配前面的 0 次或多次重复 |
| + | 匹配前面的 1 次或多次重复 |
| ? | 前面字符可选 |
| {n,m} | 最少n个,不超过m个 |
| (xyz) | 对xyz分组 |
| | | 或 |
| \ | 转义 |
| ^ | 以什么开头 |
| $ | 以什么结尾 |
# 2.1 .
'.l' => I'm Paul, can you help me.
# 2.2 [] [^]
'[Tt]he' => The car parked in the garage.
'[T]he' => The car parked in the garage.
'ar[k]' => The car parked in the garage.
'ar[ka]' => The car parked in the garage.
匹配ar开头, 并且ar后面的字符不是k的所有
'ar[^k]' => The car parked in the garage.
# 2.3 * +
匹配所有`a-z`并且出现0次或多次重复
'[a-z]*' => The car parked in the garage 21 name.
匹配出cat并且前后出现过空格0次或多次重复
'\scat\s' The fat cat sat on the concatenation.
匹配出`c`开头, c后面至少一个字符, 出现t至少一次或多次
The fat cat sat on the concatenation.
'c.+t' => The fat cat sat on the concatenation.
'c.+s' => The fat cat sat on the concatenation.
匹配he前面出现 T 0次或者1次
'[T]?he' => The car is parked in the garage.
# 2.4 {} 大括号的用法, 指一个字符或一组字符可以重复的次数
匹配数字, 长度最少为2,最大为3
'[0-9]{2,3}' => The number was 9.9997 but we rounded it off to 10.0.
// 只匹配长度为3的数字
'[0-9]{3}' => The number was 9.9997 but we rounded it off to 10.0.
// 匹配长度至少为2位的数字
'[0-9]{2,}' => The number was 9.99971 but we rounded it off to 10.0.
# 2.5 | 捕获分组
匹配出ar结尾,c或p或g开头的字符
// 分组
'(c|p|g)ar' => The car is parked in the garage.
// 不分组
'(?:c|p|g)ar' => The car is parked in the garage.
var str= 'The car is parked in the garage.'
var reg=/(c|p|g)ar/g;
var res = str.match(reg);
while(res = reg.exec(str))
{
console.log(res[1]); // 返回分组信息 c,p,g
}
[ 'car',
'c',
index: 4,
input: 'The car is parked in the garage.',
groups: undefined ]
[ 'par',
'p',
index: 11,
input: 'The car is parked in the garage.',
groups: undefined ]
[ 'gar',
'g',
index: 25,
input: 'The car is parked in the garage.',
groups: undefined ]
# 2.6 交替
匹配出the或者 c g开头ar结尾的字符
原始字符串 : The car is parked in the garage.
'(c|g)ar|the' => The car is parked in the garage.
# 2.7 转义字符
匹配出fat cat sat mat.
原始字符串: The fat cat sat on the mat.
(f|s|a).? => The fat cat sat on the mat.
# 2.8 锚点Anchors ^ $
获取到以某个字符开头的
原始字符串: The fat cat sat on the mat.
匹配The/the
'(T|t)he' => The fat cat sat on the mat.
匹配开头是T或者t的, 结尾是he的字符,^ 表示整个字符的开始字符
'^(T|t)he' => The fat cat sat on the mat.
# 2.8.1 $ 是否是匹配字符串的最后一个字符
TIP
原始字符串: The fat cat. sat. on the mat.
匹配所有的at.
'(at.)' => The fat cat. sat. on the mat.
匹配以at.结尾的
'(at.)$' => The fat cat. sat. on the mat.
# 3. 简写
. => 除了换行意外的任意字符
\w => [a-zA-Z0-9_]
\W => [^\w] 匹配非字母字符
\d => [0-9]
\D => [^\d] 匹配非数字
\s => [\t\n\f\r\p{Z}] 匹配空白字符
\S => [^\s] 匹配非空白字符
# 4. ?= ?! ?<= ?<!
TIP
原始字符串: The fat cat sat on the mat The mat.
?=匹配后面是mat的The/the
'([T|t]he)(?=\smat)' => The fat cat sat on the mat The mat.
?!匹配后面不是fat的The/the
'[T|t]he(?!\sfat)' => The fat cat sat on the mat The cat.
?<= 匹配某个东西的后面
'(?<=[T|t]he\s)(fat|mat)' => The fat cat sat on the mat.
?<! 不需要匹配某样东西的后面, 匹配不是the后面的cat
'(?<![T|t]he)(cat)' => The cat sat on cat.
# 5. i/g/m
i => 不区分大小写
g => 全局搜索
m => 多行
`i`
'/The/g' => The fat cat sat on the mat.
不区分大小写,并且全局
'/The/gi' => The fat cat sat on the mat.
全局搜索
'/.(at)/' => The fat cat sat on the mat.
'/.(at)/g' => The fat cat sat on the mat.
// 匹配多行
'/.at$/g' => The fat cat sat
on the `mat`
'/.at$/gm' => The fat cat `sat`
on the `mat`
# 6. 贪婪匹配/懒惰匹配
TIP
贪婪匹配:
'(.*at)' => The fat cat sat on the mat.
懒惰匹配:
'(.*?at)' => The fat cat sat on the mat.