1. Character metacharacters
| [ ... ] |
matches any character in the list |
| [ ^... ] |
matches any character not in the list |
| . |
Matches any character except carriage return and line feed |
| \w |
Equivalent to [ A-Za-z0-9_ ], matching any letters, numbers, underline characters, such characters are also called word characters. |
| \W |
Equivalent to [ ^A-Za-z0-9_ ], does not match any letters, numbers, underscore characters. |
| \d |
Equivalent to [ 0-9 ], matches any single digit character. |
| \D |
Equivalent to [ ^0-9 ], matches any single character except digits. |
| \s |
Match whitespace characters, which refer to spaces, tab characters, and carriage return and line feed characters. |
| \S |
Matches any non-whitespace character. |
2. Repeating metacharacters
| x? |
Matches 0 or 1 x. |
| x+ |
Match one or more x, i.e. match at least one x. |
| x* |
Match 0 or more x's. |
| x{ n } |
Matches n x's. |
| x{ n, } |
match n x |
| x{ n,m } |
Match at least n x and at most m x, that is, match n to m x. |
3. Positioning meta characters
| ^ |
match must occur at the beginning of the string or the beginning of the line |
| $ |
A match must occur at: end of string, before \n at end of string, or end of line. |
| \b |
matches the start or end of a word |
| \B |
matches the start or end of a non-word |
| x( ? = y ) |
Positive positive check. Only when x is followed by y, can x be matched successfully. |
| x( ? ! y ) |
Positive negative lookup. Only when x is not followed by y, can x be matched successfully. |
| （ ?<= x ）y: |
Reverse affirmative precheck. Only when y is preceded by x, the match y is successful. Not supported in JS. (Reverse, etc., add < before forward etc.) |
| （ ?< ! x ）y: |
Reverse negative lookup. Only when y is not preceded by x, y is matched successfully. Not supported in JS. (The reverse is not equal, add < before the forward etc.) |
4. Grouping and replacing characters
| x | y |
match x or y |
| （ content ） |
Back reference, handle the subexpression content as a whole, the role of parentheses is equivalent to the role of parentheses in algebra, and save the captured submatches in \1, \2, ... and $1, $2, ......middle. For example: /a(bc)+/ |
| (?: content) |
Group subpatterns, but do not capture subpatterns. It works similarly to (content) and is called a memoryless match. |
| \1，\2，\3，... |
In the regular expression, respectively contain strings matching the first backreference, the second backreference, and the third backreference in the regular expression. |
| $1，$2，$3，... |
In the replacement, include the first backreference and the second backreference in the regular expression, respectively. The third backreference matches the string. |
5. Special characters
Special characters are those characters that are not easy to express directly in writing or input directly using the keyboard
| \ 0 |
Match the null character, the corresponding hexadecimal value is \x00 |
| \ b |
Match the backspace character, the corresponding hexadecimal value is \x08 |
| \ n |
Match a newline character, the corresponding hexadecimal value is \x0A |
| \ r |
Match the carriage return character, the corresponding hexadecimal is \x0D |
| \ f |
Match the form feed character, the corresponding hexadecimal is \x0C |
| \ t |
Matches the tabulation (TAB) character, corresponding to both the horizontal tab character \x09 and the vertical tab character \x0B |
| \xhh |
Matches characters represented by 2 hexadecimal digits |
| \ uhhhh |
Matches characters represented by 4 hexadecimal digits, which are Unicode characters |
| \ cchar |
Match named control characters |
6. Characters that need to be escaped
. * + ( ) $ / \ ? [ ] ^ { } - ! < >
7. Common regular expressions
| [ \u4e00-\u9fa5 ] |
match any character |
| [ 1- 9 ]?[ 0-9 ] | 100 |
Matches numbers from 0-100 |
| \n [ \s| ] * \r |
Regular expression to match empty lines |