Regular Expression references

The following table shows a complete list of metacharacters and their behaviors in the context of a regular expression:
\ Mark the next character as a special character, a literal character, a back reference, or an octal escape character.
^ Matches the start position of the input string. If the multiline attribute of the Regexp object is set, ^ matches the position after '\ n' or' \ R.
$ Matches the end position of the input string. If the multiline attribute of the Regexp object is set, $ also matches the position before '\ n' or' \ R.
* Matches the previous subexpression zero or multiple times.
+ Match the previous subexpression once or multiple times. + Is equivalent to {1 ,}.
? Match the previous subexpression zero or one time .? It is equivalent to {0, 1 }.
{N} n is a non-negative integer that matches the specified n times.
{N ,}n is a non-negative integer and matches at least N times.
Both {n, m} m and n are non-negative integers, where n <= m. Match at least N times and at most m times. There must be no space between a comma and two numbers.
? When this character is followed by any other delimiter (*, + ,?, The matching mode after {n}, {n ,}, {n, m}) is not greedy. The non-Greedy mode matches as few searched strings as possible, while the default greedy mode matches as many searched strings as possible.
. Match any single character except "\ n. To match any character including '\ n', use a pattern like' [. \ n.
(Pattern) matches pattern and obtains this match.
(? : Pattern) matches pattern but does not get the matching result. That is to say, this is a non-get match and is not stored for future use.
(? = Pattern) Forward pre-query: matches the search string at the beginning of any string that matches pattern. This is a non-get match, that is, the match does not need to be obtained for future use.
(?! Pattern) negative pre-query, and (? = Pattern ).
X | y matches X or Y.
[Xyz] Character Set combination.
[^ XYZ] combination of negative character sets.
[A-Z] character range, matching any character in the specified range.
[^ A-Z] The negative character range matches any character that is not within the specified range.
\ B matches a word boundary, that is, the position between a word and a space.
\ B matches non-word boundaries.
\ CX matches the control characters specified by X.
\ D matches a numeric character. It is equivalent to [0-9].
\ D matches a non-numeric character. It is equivalent to [^ 0-9].
\ F matches a break. It is equivalent to \ x0c and \ Cl.
\ N matches a linefeed. It is equivalent to \ x0a and \ CJ.
\ R matches a carriage return. It is equivalent to \ x0d and \ cm.
\ S matches any blank characters, including spaces, tabs, and page breaks. It is equivalent to [\ f \ n \ r \ t \ v].
\ S matches any non-blank characters. It is equivalent to [^ \ f \ n \ r \ t \ v].
\ T matches a tab. It is equivalent to \ x09 and \ CI.
\ V matches a vertical tab. It is equivalent to \ x0b and \ ck.
\ W matches any word characters that contain underscores. It is equivalent to [A-Za-z0-9 _].
\ W matches any non-word characters. It is equivalent to [^ A-Za-z0-9 _].
\ XN matches n, where N is the hexadecimal escape value. The hexadecimal escape value must be determined by the length of two numbers.
\ Num matches num, where num is a positive integer. References to the obtained matching.
\ N identifies an octal escape value or a backward reference. If at least N subexpressions are obtained before \ n, n is a backward reference. Otherwise, if n is an octal digit (0-7), n is an octal escape value.
\ Nm identifies an octal escape value or a backward reference. If there are at least is preceded by at least nm obtained subexpressions before \ nm, then nm is backward reference. If at least N records are obtained before \ nm, n is a backward reference followed by text M. If none of the preceding conditions are met, if n and m are Octal numbers (0-7), \ nm matches the octal escape value nm.
\ NML if n is an octal digit (0-3) and both M and l are octal digits (0-7), the octal escape value NML is matched. \ UN matches n, where n is a Unicode character represented by four hexadecimal numbers.

The following is a common Regular Expression --
Verification number: ^ [0-9] * $
Verify the n-digit number: ^ \ D {n} $
Verify at least N digits: ^ \ D {n,} $
Verify M-N digits: ^ \ D {m, n} $
Verify the number starting with zero or zero: ^ (0 | [1-9] [0-9] *) $
Verify the positive number of two decimal places: ^ [0-9] + (. [0-9] {2 })? $
Verify the positive number of 1-3 decimal places: ^ [0-9] + (. [0-9] {1, 3 })? $
Verify a non-zero positive integer: ^ \ +? [1-9] [0-9] * $
Verify a non-zero negative integer: ^ \-[1-9] [0-9] * $
Verify non-negative integer (positive integer + 0) ^ \ D + $
Verify non-positive integer (negative integer + 0) ^ (-\ D +) | (0 +) $
3 characters for verification: ^. {3} $
Verify a string consisting of 26 English letters: ^ [A-Za-Z] + $
Verify a string consisting of 26 uppercase letters: ^ [A-Z] + $
Verify a string consisting of 26 lower-case letters: ^ [A-Z] + $
Verify a string consisting of digits and 26 English letters: ^ [A-Za-z0-9] + $
Verify a string consisting of digits, 26 English letters, or underscores: ^ \ W + $
Verify User Password: ^ [A-Za-Z] \ W {5, 17} $ the correct format is: it must start with a letter and be between 6 and 18 characters. It can only contain characters, numbers, and underscores.
Check whether ^ % & ',; =? $ \ "And other characters: [^ % & ',; =? $ \ X22] +
Verify Chinese characters: ^ [\ u4e00-\ u9fa5], {0,} $
Verify email address: ^ \ W + [-+.] \ W +) * @ \ W + ([-.] \ W + )*\. \ W + ([-.] \ W +) * $
Verify interneturl: ^ http: // ([\ W-] + \.) + [\ W-] + (/[\ W -./? % & =] *)? $; ^ [A-Za-Z] +: // (W + (-W +) *) (. (W + (-W + )*))*(? S *)? $
Verification phone number: ^ (\ D {3, 4} \) | \ D {3, 4 }-)? \ D {7,8} $: -- the correct format is: XXXX-XXXXXXX, XXXX-XXXXXXXX, XXX-XXXXXXX, XXX-XXXXXXXX, xxxxxxx, XXXXXXXX.
Verify the ID card number (15 or 18 digits): ^ \ D {15} | \ D {} 18 $
12 months of verification: ^ (0? [1-9] | 1 [0-2]) $ the correct format is: "01"-"09" and "1" "12"
31 days of verification for a month: ^ (0? [1-9]) | (1 | 2) [0-9]) | 30 | 31) $ the correct format is: 01, 09, 1, 31.
Integer: ^ -? \ D + $
Non-negative floating point number (Positive floating point number + 0): ^ \ D + (\. \ D + )? $
Positive floating point number ^ ([0-9] + \. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * \. [0-9] +) | ([0-9] * [1-9] [0-9] *) $
Non-Positive floating point number (negative floating point number + 0) ^ (-\ D + (\. \ D + )?) | (0 + (\. 0 + )?)) $
Negative floating point number ^ (-([0-9] + \. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * \. [0-9] +) | ([0-9] * [1-9] [0-9] *) $
Floating Point Number ^ (-? \ D +) (\. \ D + )? $