Regular expression matching Chinese characters:
Match double byte characters (including Chinese characters)
Application: calculate the length of the string (a double byte character length meter 2, ASCII character count 1)
Regular expression matching empty lines:
Regular expression matching HTML tag:
Regular expressions that match leading and trailing spaces:
Application: there is no trim function like VBScript in J avascript. We can use this expression to implement it, as follows:
{
return this.replace(/(^\s*)|(\s*$)/g, “”);
}
Using regular expression to decompose and transform IP address
The following is a JavaScript program that uses regular expressions to match IP addresses and converts IP addresses to corresponding values:
{
Re = / (- D +) \. [D +) \. (\ D +) \. (\ D +) / g / / regular expression matching IP address
if(re.test(ip))
{
return RegExp.$1*Math.pow(255,3))+RegExp.$2*Math.pow(255,2))+RegExp.$3*255+RegExp.$4*1
}
else
{
throw new Error(“Not a valid IP address!”)
}
}
However, if the above program does not use regular expressions, it may be simpler to use split function to decompose directly. The program is as follows:
ip=ip.split(“.”)
Alert (“IP value is: + (IP [0] * 255 * 255 * 255 + IP [1] * 255 * 255 + IP [2] * 255 + IP [3] * 1))
Regular expression matching email address:
Regular expression matching URL of web address:
Using regular expressions to remove repeated characters in a string: [* Note: This program is not correct]
var s1=s.replace(/(.).*\1/g,”$1″)
var re=new RegExp(“[“+s1+”]”,”g”)
var s2=s.replace(re,””)
Alert (S1 + S2) / / the result is: abcefgi
*Note
===============================
If var s = abacabefggeeii “
The result is wrong, the result is: abeiccfg
The power of regular expressions is limited
===============================
I originally posted an expression on CSDN to find an expression to remove duplicate characters, but I didn’t find it. This is the simplest method I can think of. The idea is to use the backward reference to extract the repeated characters, and then use the repeated characters to establish a second expression, get the non repeated characters, and connect the two. This method may not work for strings that require character order.
A JavaScript program that uses regular expressions to extract the file name from the URL address. The following result is page1
s=s.replace(/(.*\/){ 0, }([^\.]+).*/ig,”$2″)
alert(s)
Using regular expressions to restrict the input content of text box in web form:
Use regular expression to restrict Chinese input only:
Use regular expressions to restrict the input of full width characters only:
Use regular expressions to restrict you to only enter numbers:
Use regular expression to restrict the input of only numbers and English:
Match nonnegative integers (positive integers + 0)
Match positive integers
Match non positive integers (negative integers + 0)
Match negative integers
Match integer
Match non negative floating point numbers (positive float + 0)
Match positive floating point numbers
Match non positive floating point numbers (negative float + 0)
Match negative floating point numbers
Matching floating point numbers
Matches a string of 26 English letters
Matches a string of 26 uppercase letters
Matches a string of 26 lowercase letters
Matches a string of numbers and 26 English letters
Matches a string of numbers, 26 letters, or underscores
Match email address
Match URL
Match HTML tag
Visual Basic & C# Regular Expression
1. Confirm valid email format
The following example uses static Regex.IsMatch Method to verify that a string is in a valid e-mail format. The isvalidmail method returns true if the string contains a valid e-mail address, false otherwise, but no other action is taken. You can use isvalidmail to store the address in the database or display it in the application ASP.NET Page to filter out email addresses that contain invalid characters.
[Visual Basic]
‘ Return true if strIn is in valid e-mail format.
Return Regex.IsMatch(strIn, (“^([\w-\.]+)@((\[[0-9]{ 1,3 }\.[0-9]{ 1,3 }\.[0-9]{ 1,3 }\.)|(([\w-]+\.)+))([a-zA-Z]{ 2,4 }|[0-9]{ 1,3 })(\]?)$”)
End Function
[C#]
{
// Return true if strIn is in valid e-mail format.
return Regex.IsMatch(strIn, @”^([\w-\.]+)@((\[[0-9]{ 1,3 }\.[0-9]{ 1,3 }\.[0-9]{ 1,3 }\.)|(([\w-]+\.)+))([a-zA-Z]{ 2,4 }|[0-9]{ 1,3 })(\]?)$”);
}
2. Clean the input string
The following code example uses static Regex.Replace Method to extract invalid characters from a string. You can use the cleaninput method defined here to remove potentially harmful characters entered in the text fields of forms that accept user input. Cleaninput returns a string after removing all non alphanumeric characters except @, – (hyphen), and. (period).
[Visual Basic]
‘ Replace invalid characters with empty strings.
Return Regex.Replace(strIn, “[^\w\[email protected]]”, “”)
End Function
[C#]
{
// Replace invalid characters with empty strings.
return Regex.Replace(strIn, @”[^\w\[email protected]]”, “”);
}
3. Change date format
The following code example uses Regex.Replace Method to replace the date form of mm / DD / yy with the date form DD mm YY.
[Visual Basic]
Return Regex.Replace(input, _
“\b(?<month>\d{ 1,2 })/(?<day>\d{ 1,2 })/(?<year>\d{ 2,4 })\b”, _
“${ day }-${ month }-${ year }”)
End Function
[C#]
{
return Regex.Replace(input,”\\b(?<month>\\d{ 1,2 })/(?<day>\\d{ 1,2 })/(?<year>\\d{ 2,4 })\\b”,”${ day }-${ month }-${ year }”);
}
Regex replacement mode
This example shows how to use the Regex.Replace The named reverse reference is used in the replacement pattern of. Where the replacement expression ${day} is inserted by (?) ）The substring captured by the group.
There are several static functions that allow you to use regular expression operations without creating an explicit regular expression object Regex.Replace Function is one of them. If you don’t want to keep compiled regular expressions, this will be convenient for you
4. Extract URL information
The following code example uses Match.Result To extract the protocol and port number from the URL. For example“ http://www.penner.cn :8080…… Will return“ http:8080 ”。
[Visual Basic]
Dim r As New Regex(“^(?<proto>\w+)://[^/]+?(?<port>:\d+)?/”, _
RegexOptions.Compiled)
Return r.Match(url).Result(“${ proto }${ port }”)
End Function
[C#]
{
Regex r = new Regex(@”^(?<proto>\w+)://[^/]+?(?<port>:\d+)?/”,
RegexOptions.Compiled);
return r.Match(url).Result(“${ proto }${ port }”);
}
The regular expression of a password containing only letters and numbers, not less than 6 digits, and containing both numbers and letters
In C ා, this can be used to express:
An algorithm program that splits the path string into two parts: root directory and subdirectory. Consider the path format as follows: C: ﹣ AA ﹣ BB ﹣ CC, \, ftp://aa.bb/cc The above paths will be split into: C: \, AA and AA / BB / cc, \ \ AA and / BB / cc, FTP: / / and aa.bb/cc It is implemented with JavaScript as follows:
var regPathParse=/^([^\\^\/]+[\\\/]+|\\\\[^\\]+)(.*)$/
if(regPathParse.test(strFolder))
{
strRoot=RegExp.$1
strSub=RegExp.$2
}