Regular expression java PHP some conversions of some commonly used regular expression characters

Match double-byte characters (including Chinese characters): [^x00-xff]
Application: Calculate the length of a string (the length of a double-byte character counts as 2, and the ASCII character counts as 1)
String.prototype.len=function( ){return this.replace([^x00-xff]/g,"aa").length;}
Regular expression to match blank lines: n[s| ]*r
Regular expression to match HTML tags: / <(.*)>.*|<(.*) />/
Regular expression matching leading and trailing spaces: (^s*)|(s*$)
Application: javascript There is no trim function like vbscript, we can use this expression to achieve it, as follows:
String.prototype.trim = function() {
return this.replace(/(^s*)|(s*$) /g, "");
}
Use regular expressions to decompose and convert IP addresses:
The following is a javascript program that uses regular expressions to match IP addresses and convert IP addresses into corresponding values:
function IP2V(ip) {
re=/(d+).(d+).(d+).(d+)/g //Regular expression matching IP address
if(re.test(ip)) {
return RegExp.*Math.pow( 255,3))+RegExp.*Math.pow(255,2))+RegExp.*255+RegExp.*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 the split function to decompose it directly. The program is as follows:
var ip="10.100.20.168"
ip=ip.split(".")
alert(" The IP value is: "+(ip[0]*255*255*255+ip[1]*255*255+ip[2]*255+ip[3]*1))
　 Regular expression matching email address ： w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*
　 Regular expression matching URL: http://([w-]+ .)+[w-]+(/[w- ./?%&=]*)?
Algorithm program for removing repeated characters from a string using regular expressions:
var s="abacabefgeeii"
var s1= s.replace(/(.).*/g,"")
var re=new RegExp("["+s1+"]","g")
var s2=s.replace(re,"")
alert(s1+s2) //The result is: abcefgi
A javascript program that uses regular expressions to extract file names from URL addresses. The following result is page1
s="http://www.9499.net/page1.htm"
s=s.replace(/(.*/)([^.]+).*/ig,"")
alert(s)
Use regular expressions to limit the input content of the text box in the web form:
Use The regular expression restricts the input of only Chinese characters:
/[^u4E00-u9FA5]/g,'')" /[^u4E00-u9FA5]/g,''))"
The regular expression restricts the input of only full-width characters. :
/[^uFF00-uFFFF]/g,'')" /[^uFF00-uFFFF]/g,''))"
Use regular expressions to limit the input of numbers only:
/[^d]/g ,'') "/[^d]/g,''))"
Use regular expressions to limit the input to numbers and English only:
/[W]/g,'') "/[^d]/g ,''))

The above introduces some conversions of some commonly used regular expression characters in regular expression java PHP, including the content of regular expression java. I hope it will be helpful to friends who are interested in PHP tutorials.