What are the regular expressions commonly used in the Internet

This article mainly introduces the regular expressions commonly used in the Internet, the article is very detailed, has a certain reference value, interested friends must read it!

Regular expressions that match Chinese characters: [\ u4e00 -\ u9fa5]

Match double-byte characters (including Chinese characters): [^\ X00 -\ xff]

Application: calculates the length of a string (a double-byte character length meter 2 ~ ASCII character counter 1)

String.prototype.len=function () {return this.replace ([^\ X00 -\ xff] / g, "aa") .length;}

Regular expression that matches blank lines:\ n [\ s |] *\ r

Regular expression that matches the HTML tag: /. * | /

Regular expression that matches leading and trailing spaces: (^\ s*) | (\ sblank $)

String.prototype.trim = function () {return this.replace (/ (^\ s *) | (\ s $) / g, ");}

Use regular expressions to decompose and translate IP addresses:

The following is a Javascript program that uses regular expressions to match IP addresses and converts IP addresses to corresponding values:

Function IP2V (ip) {re=/ (\ d+)\. (\ d+) / g / / regular expression if (re.test (ip)) {return RegExp.1 ∗ Math.pow (255) + RegExp.2*Math.pow (255) + 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, but directly use the split function to decompose it may be easier, the program is as follows:

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))

The regular expression that matches the Email address:\ W + ([- +.]\ w +) * @\ w + ([-.]\ w +) *.\ w + ([-.]\ w +) *

The regular expression that matches the URL URL: http://([\w-]+\.)+[\w-]+(/[\w-. /?% & =] *?

An algorithmic program that uses regular expressions to remove repeated characters from a string: [note: this program is incorrect, see red font]

Var s = "abacabefgeeii" var s1=s.replace (/ (.). *\ 1CMG, "$1") var re=new RegExp ("[" + S1 + "]", "g") var s2=s.replace (re, ") alert (s1+s2) / / the result is: abcefgi

= =

If var s = "abacabefggeeii"

The result is wrong, the result is: abeicfgg

The ability of regular expressions is limited

I originally posted on CSDN looking for an expression to remove repetitive characters, but I didn't find it. This is the simplest implementation I can think of. The idea is to use the backward reference to take out the characters including repetition, then create a second expression with the repeated characters, take the non-repetitive characters, and concatenate the two. This method may not apply to strings that require character order.

The javascript program that extracts the file name from the URL address with a regular expression, the following result is page1

S = "http://www.9499.net/page1.htm"s=s.replace(/(.*\/){0,}([^\.]+).*/ig,"$2")alert(s)

Use regular expressions to restrict text box input in a web form:

Use regular expressions to restrict input to Chinese only:

Onkeyup= "value=value.replace (/ [^\ u4E00 -\ u9FA5] / g text'')" onbeforepaste=clipboardData.setData ('text',clipboardData.getData (' text'). Replace (/ [^\ u4E00 -\ u9FA5] / g charge')) "

Use regular expressions to restrict the input of full-width characters:

Onkeyup=value=value.replace (/ [^\ uFF00-\ uFFFF] / gjime') "onbeforepaste=clipboardData.setData ('text',clipboardData.getData (' text') .replace (/ [^\ uFF00-\ uFFFF] / gjime'))"

Use regular expressions to limit input to numbers:

Onkeyup= "value=value.replace (/ [^\ d] / gjinger')" onbeforepaste= "clipboardData.setData ('text',clipboardData.getData (' text'). Replace (/ / [^\ d] / gjime'))"

Use regular expressions to limit input to numbers and English:

Onkeyup= "value=value.replace (/ [\ W] / GMagneur')" onbeforepaste= "clipboardData.setData ('text',clipboardData.getData (' text'). Replace (/ [^\ d] / GMagneur'))"

Application: there is no trim function like vbscript in javascript, so we can use this expression to implement it, as follows:

/ * calculates the string length and calculates non-wide characters as half a character * * @ param str * @ returns * / function gbLength (str) {return typeof str = "string"? Str.length + str.replace (/ [\ x00 -\ x7f] / g,'). Length + 1 > > 1: 0;} / * gets the substring of the specified length of the string and calculates the non-wide character as half a character * * @ param str * @ param length * @ returns * / function gbSubstr (str, length) {if (typeof str! = "string") return str; length + = length; for (var n = 0, L = str.length; n)

< L && length >

0; return str.substr +) {length-= str.charCodeAt (n) > 1272: 1;} return str.substr (0, n);} / * cut the specified length substring of the specified string. If the length exceeds the specified length, discard the last two characters and append. * * @ param str * @ param len * @ returns * / function fit_length (str, len) {len = len | | 16 If (typeof str! = = "string" | | str.length