Java basics: Common matching regular expressions and instances

Regular

Matching regular expressions for Chinese characters: [\U4E00-\U9FA5]

Match Double-byte characters (including Chinese characters): [^\x00-\xff]

Application: Computes the length of the string (a double-byte character length meter 2,ascii character 1)

String.prototype.len=function () {return This.replace ([^\x00-\xff]/g, "AA"). Length;}

A regular expression that matches a blank row: \n[\s|] *\r

Regular expression matching HTML tags:/< (. *) >.*<\/\1>|< (. *) \/>/

Matching a regular expression with a trailing space: (^\s*) | (\s*$)

Application: JavaScript does not have a trim function like VBScript, we can use this expression to implement, as follows:

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

To decompose and transform an IP address using a regular expression:

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:

function IP2V (IP) {re=/(\d+) \. ( \d+) \. (\d+) \. (\d+)/g//matching IP address regular expression 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:

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: \w+ ([-+.] \w+) *@\w+ ([-.] \w+) *\.\w+ ([-.] \w+) *

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

An algorithmic program that uses regular expressions to remove repetitive characters from a string:

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

This is the simplest way to implement an expression to remove repetitive characters.

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

s= "http://www.9499.net/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:

The regular expression limit can only be entered in Chinese: 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: 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: onkeyup= "Value=value.replace (/[^\d]/g,") "Onbeforepaste=" Clipboarddata.setdata (' text ', Clipboarddata.getdata (' text '). Replace (/[^\d]/g, ') "

Only numbers and English can be entered with regular expression restrictions: onkeyup= "Value=value.replace (/[\w]/g,") "Onbeforepaste=" Clipboarddata.setdata (' text ', Clipboarddata.getdata (' text '). Replace (/[^\d]/g, ') "