Regular expressions are often used when building websites. The following are some explanations and examples for your reference and modification:
Match numbers
"^\d+$"//Non-negative integer (positive integer + 0)
"^[0-9]*[1-9][0-9]*$"//Positive integer
"^((-\d+)|(0+))$"//Non-positive integer (negative integer + 0)
"^-[0-9]*[1-9][0-9]*$"//Negative integer
"^-?\d+$"//Integer
"^\d+(\.\d+)?$"//Non-negative floating point number (positive floating point number + 0)
"^(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]+)|([0-9]*[1-9][0-9]*))$"//Positive floating point number
"^((-\d+(\.\d+)?)|(0+(\.0+)?))$"//Non-positive floating point number (negative floating point number + 0)
"^(-((([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]+)|([0-9]*[1-9][0-9]*)))$"//Negative floating point number
"^(-?\d+)(\.\d+)?$"//Floating point number
Match letters
"^[A-Za-z]+$"//A string composed of 26 English letters
"^[A-Z]+$"//A string composed of 26 English letters capitalization
"^[a-z]+$"//A string composed of 26 English letters lowercase
"^[A-Za-z0-9]+$"//A string composed of numbers and 26 English letters
"^\w+$"//A string composed of numbers, 26 English letters or underscores
Match instance
"^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$"//email address
"^[a-zA-z]+://(\w+(-\w+)*)(\.(\w+(-\w+)*))*(\?\S*)?$"//url
/^(d{2}|d{4})-((0([1-9]{1}))|(1[1|2]))-(([0-2]([1-9]{1}))|(3[0|1]))$/ // Year-Month-Day
/^((0([1-9]{1}))|(1[1|2]))/(([0-2]([1-9]{1}))|(3[0|1]))/(d{2}|d{4})$/ // Month/Day/Year
"^([w-.]+)@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.)|(([w-]+.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(]?)$" //Emil
/^((\+?[0-9]{2,4}\-[0-9]{3,4}\-)|([0-9]{3,4}\-))?([0-9]{7,8})(\-[0-9]+)?$/ // Phone number
"^(d{1,2}|1dd|2[0-4]d|25[0-5]).(d{1,2}|1dd|2[0-4]d|25[0-5]).(d{1,2}|1dd|2[0-4]d|25[0-5]).(d{1,2}|1dd|2[0-4]d|25[0-5])$" //IP address
Other matches
Regular expression matching Chinese characters: [\u4e00-\u9fa5]
Match double-byte characters (including Chinese characters): [^\x00-\xff]
Regular expression matching blank lines: \n[\s| ]*\r
Regular expression matching HTML tags: /<(.*)>.*<\ 1="">|<(.*)>/
Regular expression matching the beginning and end spaces: (^\s*)|(\s*$)
Regular expression matching email address: \w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*
Regular expression matching URL URL: ^[a-zA-z]+://(\\w+(-\\w+)*)(\\.(\\w+(-\\w+)*))*(\\?\\S*)?$
Match whether the account is legal (beginning with letters, 5-16 bytes allowed, alphanumeric underscores allowed): ^[a-zA-Z][a-zA-Z0-9_]{4,15}$
Match domestic phone number: (\d{3}-|\d{4}-)?(\d{8}|\d{7})?
Match Tencent QQ number: ^[1-9]*[1-9][0-9]*$
Metachars and their behavior in regular expression context:
\Mark the next character as a special character, or an primitive character, or a backward reference, or an octal escape character.
^ Matches the start position of the input string. If the Multiline property of the RegExp object is set, ^ also matches the position after '\n' or '\r'.
$ Matches the end position of the input string. If the Multiline property of the RegExp object is set, $ also matches the position before '\n' or '\r'.
* Match the previous subexpression zero or multiple times
+ Match the previous subexpression once or more times. + is equivalent to {1,}.
? Match the previous subexpression zero or once. ? is equivalent to {0,1}.
{n} n is a non-negative integer that matches the determined n times.
{n,} n is a non-negative integer that matches at least n times.
{n,m} m and n are non-negative integers, where n <= m. Match at least n times and match up to m times. There cannot be spaces between commas and two numbers.
? When the character is immediately followed by any other restriction character (*, +, ?, {n}, {n,}, {n,m}), the matching pattern is non-greedy. The non-greedy pattern matches as few strings as possible, while the default greedy pattern matches as many strings as possible.
. Match any single character except "\n". To match any characters including '\n', use a pattern like '[.\n]'.
(pattern) Match pattern and get this match.
(?:pattern) Match pattern but does not get the matching result, that is, this is a non-get match and is not stored for future use.
(?=pattern) Forward pre-check, matching the lookup string at the beginning of any string matching pattern. This is a non-get match, that is, the match does not need to be retrieved for later use.
(?!pattern) Negative pre-examination, opposite to (?=pattern)
x|y matches x or y.
[xyz] Character collection.
[^xyz] Collection of negative values characters.
[a-z] Character range, matching any character within the specified range.
[^a-z] Negative value character range, matching any character that is not within the specified range.
\b Match a word boundary, which means the position between the word and space.
\B Match non-word boundaries.
\cx Matches the control characters specified by x.
\d Match a numeric character. Equivalent to [0-9].
\D Match a non-numeric character. Equivalent to [^0-9].
\f Match a page break. Equivalent to \x0c and \cL.
\n Match a newline character. Equivalent to \x0a and \cJ.
\r Match a carriage return character. Equivalent to \x0d and \cM.
\s Match any whitespace characters, including spaces, tabs, page breaks, etc. Equivalent to [ \f\n\r\t\v].
\S Match any non-whitespace characters. Equivalent to [^ \f\n\r\t\v].
\t Match a tab character. Equivalent to \x09 and \cI.
\v Match a vertical tab character. Equivalent to \x0b and \cK.
\w Match any word character that includes an underscore. Equivalent to '[A-Za-z0-9_]'.
\W Match any non-word character. Equivalent to '[^A-Za-z0-9_]'.
\xn matches n, where n is a hexadecimal escape value. The hexadecimal escape value must be the length of two numbers that are determined.
\num matches num, where num is a positive integer. Reference to the obtained match.
\n Identifies an octal escape value or a backward reference. If \n has at least n obtained subexpressions before, n is a backward reference. Otherwise, if n is an octal number (0-7), n is an octal escape value.
\nm Identifies an octal escape value or a backward reference. If \nm has at least obtained subexpressions before is preceded by at least nm, nm is a backward reference. If there are at least n retrieves before \nm, n is a backward reference followed by the literal m. If none of the previous conditions are satisfied, if both n and m are octal numbers (0-7), then \nm will match the octal escape value nm.
\nml If n is an octal number (0-3), and both m and l are octal numbers (0-7), the octal escape value nml is matched.
\un matches n, where n is a Unicode character represented by four hexadecimal numbers.
Regular expression matching Chinese characters: [u4e00-u9fa5]
Match double-byte characters (including Chinese characters): [^x00-xff]
Regular expression matching blank lines: n[s| ]*r
Regular expression matching HTML tags: /<(.*)>.*|<(.*)>/
Regular expression matching the beginning and end spaces: (^s*)|(s*$)
Regular expression matching the email address: w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*
Regular expression matching URL: http://([w-]+.)+[w-]+(/[w- ./?%&=]*)?
Use regular expressions to restrict the input content in the text box in the web form:
Use regular expressions to restrict only Chinese: onkeyup="value=(/[^u4E00-u9FA5]/g,'')" onbeforepaste="('text',('text').replace(/[^u4E00-u9FA5]/g,''))"
Use regular expressions to restrict only full-width characters: onkeyup="value=(/[^uFF00-uFFFF]/g,'')" onbeforepaste="('text',('text').replace(/[^uFF00-uFFFF]/g,''))"
Use regular expressions to limit only numeric input: onkeyup="value=(/[^d]/g,'') "onbeforepaste="('text',('text').replace(/[^d]/g,''))"
Use regular expressions to restrict only numeric and English: onkeyup="value=(/[W]/g,'') "onbeforepaste="('text',('text').replace(/[^d]/g,''))"
Some commonly used regular examples
1. Non-negative integer: ^\d+$
2. Positive integer: ^[0-9]*[1-9][0-9]*$
3. Non-positive integer: ^((-\d+)|(0+))$
4. Negative integer: ^-[0-9]*[1-9][0-9]*$
5. Integer: ^-?\d+$
6. Non-negative floating point number: ^\d+(\.\d+)?$
7. 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]*))$
8. Non-positive floating point number: ^((-\d+\.\d+)?)|(0+(\.0+)?))$
9. Negative floating point number: ^(-(((regular formula for positive floating point number)))$
10. English string: ^[A-Za-z]+$
11. English capital string: ^[A-Z]+$
12. English lowercase string: ^[a-z]+$
13. English character string: ^[A-Za-z0-9]+$
14. Underlined English numbers: ^\w+$
15. E-mail address: ^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$
16、URL：^[a-zA-Z]+://(\w+(-\w+)*)(\.(\w+(-\w+)*))*(\?\s*)?$
Or: ^http:\/\/[A-Za-z0-9]+\.[A-Za-z0-9]+[\/=\?%\-&_~`@[\]\':+!]*([^<>\"\"])*$
17. Postal code: ^[1-9]\d{5}$
18. Chinese: ^[\u0391-\uFFE5]+$
19. Phone number: ^((\(\d{2,3}\))|(\d{3}\-))?(\(0\d{2,3}\)|0\d{2,3}-)?[1-9]\d{6,7}(\-\d{1,4})?$
20. Mobile phone number: ^((\(\d{2,3}\))|(\d{3}\-))?13\d{9}$
21. Double-byte characters (including Chinese characters): ^\x00-\xff
22. Match the beginning and end spaces: (^\s*)|(\s*$)(trim function like vbscript)
23. Match HTML tags: <(.*)>.*<\ 1="">|<(.*)>
24. Match empty lines: \n[\s| ]*\r
25. The network link in the extract information: (h|H)(r|R)(e|E)(f|F) *= *('|")?(\w|\\\|/|\.)+('|"| *|>)?
26. The email address in the extracted information: \w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*
27. The image link in the extracted information: (s|S)(r|R)(c|C) *= *('|")?(\w|\\\|/|\.)+('|"| *|>)?
28. The IP address in the extracted information: (\d+)\.(\d+)\.(\d+)\.(\d+)\.(\d+)
29. Chinese mobile phone number extracted from the information: (86)*0*13\d{9}
30. Chinese fixed phone number extracted from the information: (\(\d{3,4}\)|\d{3,4}-|\s)?\d{8}
31. Extract Chinese phone numbers (including mobile and landline phones) in the information: (\(\d{3,4}\)|\d{3,4}-|\s)?\d{7,14}
32. Chinese postal code in the extract information: [1-9]{1}(\d+){5}
33. Extract floating point numbers (i.e. decimals) in the information: (-?\d*)\.?\d+
34. Extract any number in the information: (-?\d*)(\.\d+)?
35、IP：(\d+)\.(\d+)\.(\d+)\.(\d+)
36. Phone area code: /^0\d{2,3}$/
37. Tencent QQ number: ^[1-9]*[1-9][0-9]*$
38. Account number (beginning with letters, 5-16 bytes allowed, alphanumeric underscores allowed): ^[a-zA-Z][a-zA-Z0-9_]{4,15}$
39. Chinese, English, numbers and underscores: ^[\u4e00-\u9fa5_a-zA-Z0-9]+$
Attached
Regular expression matching Chinese characters: [\u4e00-\u9fa5]
Match double-byte characters (including Chinese characters): [^\x00-\xff]
Regular expression matching blank lines: \n[\s| ]*\r
Regular expression matching HTML tags: /<(.*)>.*<\ 1="">|<(.*)>/
Regular expression matching the beginning and end spaces: (^\s*)|(\s*$)
Regular expression matching IP address: /(\d+)\.(\d+)\.(\d+)\.(\d+)/g //
Regular expression matching email address: \w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*
Regular expression matching URL: http://(/[\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?
sql statement: ^(select|drop|delete|create|update|insert).*$