Characters, descriptions, and simple application examples of regular expressions.

Characters, descriptions, and simple application examples of regular expressions.

 

Characters and their meanings

Character meaning

\ Escape character, escape a character with special functions into a common character

^ Match the start position of the string

$ End position of matching string

* Match the previous zero or multiple subexpressions

+ Match the previous subexpression once or multiple times

? Match the subexpression of the previous zero multiple times

{N} n is a non-negative integer that matches the previous n subexpressions.

{N ,}n is a non-negative integer. It must match at least n subexpressions.

{N, m} m, n are all non-negative integers, where n <= m, matches at least n times and can match up to m times

? When following other delimiters (*, + ,?, {N}, {n ,},{ n, m}), the matching mode matches as few strings as possible.

. Match any single character except "\ n"

(Pattern) matches pattern and obtains this match.

(? : Pattern) matches pattern but does not get the matching result.

(? = Pattern) Forward pre-query, matching the search string at the beginning of any string that matches pattern

(?! Pattern) negative pre-query, matching the search string at the beginning of any string that does not match pattern

X | y matches x or y

[Xyz] match any character contained

[^ Xyz] match any character not included

[A-z] matches any character in the specified range

[^ A-z] match 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 match non-word boundary

\ D matches a numeric character, which is equivalent to [0-9 ].

\ D matches a non-numeric character, which is equivalent to [^ 0-9]

\ F matches a newline

\ N matches a linefeed.

\ R matches a carriage return.

\ S matches any blank characters, including spaces, tabs, and page breaks.

\ S matches any non-blank characters

\ T matches a tab

\ V matches a vertical tab.

\ W matches any word characters that contain underscores. Equivalent to [a-zA-Z0-9 _]

\ W matches any non-word characters. Equivalent to [^ a-zA-Z0-9 _]

 

Use the regular exec Method for front-end js verification. The Code is as follows:

1 
 
The background uses regular expressions and the namespace using System. Text. RegularExpressions must be introduced. The static method IsMatch () of Regex is used. The Code is as follows:
1 protected void Button_Click (object sender, EventArgs e) 2 {3 string patten = @ "^ \ d {8} $"; 4 Regex regex = new Regex (patten ); 5 string text = TextBox1.Text. trim (); 6 if (! Regex. isMatch (text) 7 {8 ClientScript. registerStartupScript (ClientScript. getType (), "", "<script> alert ('input is not an 8-digit number ') </script>"); 9} 10}