A regular expression that matches a Chinese character:
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Match Double-byte characters (including Chinese characters):
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Application: Computes the length of the string (a double-byte character length meter 2,ascii character 1)
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String.prototype.len=function () {return This.replace ([^\x00-\xff]/g, "AA"). Length;}
A regular expression that matches a blank row:
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A regular expression that matches an HTML tag:
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/< (. *) >.*<\/\1>|< (. *) \/>/
A regular expression that matches a trailing space:
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Application: There is no trim function like V bscript in J Avascript, we can use this expression to implement, as follows:
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String.prototype.trim = function ()
{
Return This.replace (/(^\s*) | ( \s*$)/g, "");
}
Decomposition and conversion of IP addresses with regular expressions
The following is a JavaScript program that uses a regular expression to match an IP address and converts an IP address to a corresponding numeric value:
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function IP2V (IP)
{
re=/(\d+) \. (\d+) \. (\d+) \. (\d+)/g//matching the regular expression of the IP address
if (Re.test (IP))
{
Return Regexp.$1*math.pow (255,3)) +regexp.$2*math.pow (255,2)) +regexp.$3*255+regexp.$4*1
}
Else
{
throw new Error ("not a valid IP address!")
}
}
However, if the above program does not use a regular expression, and the split function directly to decompose may be simpler, the program is as follows:
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var ip= "10.100.20.168"
Ip=ip.split (".")
Alert ("IP value is:" + (IP[0]*255*255*255+IP[1]*255*255+IP[2]*255+IP[3]*1))
Regular expression matching an email address:
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\w+ ([-+.] \w+) *@\w+ ([-.] \w+) *\.\w+ ([-.] \w+) *
A regular expression that matches the URL of the URL:
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http://([\w-]+\.) +[\w-]+ (/[\w-/?%&=]*)?
An algorithmic program that uses regular expressions to remove repetitive characters from a string: [* Note: This program is incorrect]
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var s= "Abacabefgeeii"
var s1=s.replace (/(.). *\1/g, "$")
var re=new RegExp ("[" +s1+ "]", "G")
var s2=s.replace (Re, "")
Alert (S1+S2)//Result: ABCEFGI
* Note
===============================
If var s = "Abacabefggeeii"
The result is wrong, the result is: ABEICFGG
The ability of regular expressions is limited
===============================
I used to post on the csdn to find an expression to achieve the elimination of repeated characters, and ultimately did not find, this is the simplest way I can think of implementation. The idea is to use a back reference to take out the characters that contain duplicates, and then to create a second expression with a repeating character, with a concatenation of the characters that are not repeated. This method may not apply to strings that are required for character order.
You have to use regular expressions to extract the filename from the URL address of the JavaScript program, the following result is Page1
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S= "Http://blog.penner.cn/page1.htm"
S=s.replace (/(. *\/) {0,} ([^\.] +). */ig, "$"
Alert (s)
Use regular expressions to restrict the entry of text boxes in a Web page's form:
Only Chinese can be entered with regular expression restrictions:
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Onkeyup= "Value=value.replace (/[^\u4e00-\u9fa5]/g,") "Onbeforepaste=" Clipboarddata.setdata (' text ', Clipboarddata.getdata (' text '). Replace (/[^\u4e00-\u9fa5]/g, ') "
Only full-width characters can be entered with regular expression restrictions:
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Onkeyup= "Value=value.replace (/[^\uff00-\uffff]/g,") "Onbeforepaste=" Clipboarddata.setdata (' text ', Clipboarddata.getdata (' text '). Replace (/[^\uff00-\uffff]/g, ') "
Only numbers can be entered with regular expression restrictions:
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Onkeyup= "Value=value.replace (/[^\d]/g,") "Onbeforepaste=" Clipboarddata.setdata (' text ', Clipboarddata.getdata (' Text '). Replace (/[^\d]/g, ') "
You can only enter numbers and English with regular expression restrictions:
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Onkeyup= "Value=value.replace (/[\w]/g,") "Onbeforepaste=" Clipboarddata.setdata (' text ', Clipboarddata.getdata (' Text '). Replace (/[^\d]/g, ') "
Match nonnegative integer (positive integer + 0)
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Match positive integer
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Match a non positive integer (negative integer + 0)
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Match a negative integer
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Match integer
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matching nonnegative floating-point numbers (positive floating-point number + 0)
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Matching positive floating-point numbers
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^ ([0-9]+\. [0-9]*[1-9][0-9]*) | ([0-9]*[1-9][0-9]*\. [0-9]+) | ([0-9]*[1-9][0-9]*)] $
Matching non-positive floating-point numbers (negative floating-point number + 0)
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^ ((-\d+ (\.\d+)?) | (0+ (\.0+)) $
Matching negative floating-point numbers
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^ (-([0-9]+\. [0-9]*[1-9][0-9]*) | ([0-9]*[1-9][0-9]*\. [0-9]+) | ([0-9]*[1-9][0-9]*))] $
Matching floating-point numbers
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Match a string of 26 English letters
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Match a string of 26 uppercase letters
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Match a string consisting of 26 lowercase letters
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Match a string of numbers and 26 English letters
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Match a string of numbers, 26 English letters, or underscores
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Match email address
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^[\w-]+ (\.[ \w-]+) *@[\w-]+ (\.[ \w-]+) +$
Match URL
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^[a-za-z]+://Match (\w+ (-\w+) *) (\. ( \w+ (-\w+) *)) * (\?\s*)? $
Match HTML tag
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<\s* (\s+) (\s[^>]*)?> (. *?) <\s*\/\1\s*>
Visual Basic & C # Regular Expression
1. Confirm valid e-mail format
The following example uses the static Regex.IsMatch method to verify whether a string is a valid e-mail format. If the string contains a valid e-mail address, the IsValidEmail method returns True, otherwise it returns false without taking any other action. You can use IsValidEmail to filter e-mail addresses that contain invalid characters before an application stores the address in a database or displays it in a asp.net page.
[Visual Basic]
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Function IsValidEmail (Strin as String) as Boolean
' Return True if Strin are 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 #]
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BOOL IsValidEmail (String strin)
{
Return true if Strin are in valid e-mail format.
Return Regex.IsMatch (Strin, @ "^" ^ [\w-\.] +) @ (\[[0-9]{1,3}\. [0-9] {1,3}\. [0-9] {1,3}\.) | (([\w-]+\.) +)) ([a-za-z]{2,4}| [0-9] {1,3}) (\]?) $");
}
2. Clean the input string
The following code example uses the static Regex.Replace method to extract invalid characters from a string. You can use the CleanInput method defined here to clear out potentially harmful characters that are entered in the Text field of a form that accepts user input. CleanInput returns a string after all non-alphanumeric characters except the @,-(hyphen) and. (period) are cleared.
[Visual Basic]
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Function CleanInput (Strin As String) as String
' Replace invalid characters with empty strings.
Return Regex.Replace (Strin, "[^\w\.@-]", "")
End Function
[C #]
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String CleanInput (String strin)
{
Replace invalid characters with empty strings.
Return Regex.Replace (Strin, @ "[^\w\.@-]", "");
}
3. Change date format
The following code example uses the Regex.Replace method to replace the Mm/dd/yy date form with the Dd-mm-yy date form.
[Visual Basic]
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Function mdytodmy (input as String) as String
return Regex.Replace (Input, _
"\b (? <month>\d{1,2})/(? <day>\d{1,2})/(? <year>\d{2,4}) \b", _
"${Day}-${month}-${year}")
End Function
[C #]
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String mdytodmy (String input)
{
return Regex.Replace (Input, "\\b (? <month>\\d{1,2})/(? <day>\\d{1,2})/(? <year>\\d{2,4}) \\b", "${ Day}-${month}-${Year} ");
}
Regex substitution mode
This example shows how to use a named reverse reference in Regex.Replace replacement mode. Where the substitution expression ${Day} Inserts a substring captured by the (?...) group.
There are several static functions that allow you to use a regular expression operation without creating an explicit regular expression object, and the Regex.Replace function is one of them. This will be convenient if you do not want to keep the compiled regular expressions
4. Extract URL Information
The following code example uses Match.result to extract the protocol and port number from the URL. For example, "http://www.penner.cn:8080 ... will return "http:8080".
[Visual Basic]
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Function Extension (URL As String) as String
Dim R as New Regex ("^" <proto>\w+)://[^/]+? <port>:\d+)?/", _
regexoptions.compiled)
return R.match (URL). Result ("${Proto}${Port}")
End Function
[C #]
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String Extension (string url)
{
Regex r = new Regex (@ "^ <proto>\w+)://[^/]+? <port>:\d+)?/",
regexoptions.compiled);
return R.match (URL). Result ("${Proto}${Port}");
}
Regular expressions with letters and numbers, no less than 6 digits, and passwords contained in numeric letters
In C #, you can use this to represent:
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An algorithmic program that will need to split the path string into two parts of the root and subdirectory, taking into account the path format: C:\AA\BB\CC, \\AA\BB\CC, ftp://aa.bb/cc the above paths will be split into: C:\ and AA\BB\CC, \\aa and \bb\ CC, ftp://and AA.BB/CC are implemented using JavaScript as follows:
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var strroot,strsub
var regpathparse=/^ ([^\\^\/]+[\\\/]+|\\\\[^\\]+) (. *) $/
if (Regpathparse.test (strfolder))
{
Strroot=regexp.$1
Strsub=regexp.$2
}
