Some commonly used regular expressions in PHP

Regular expression for matching Chinese characters: [u4e00-u9fa5]

Matching double-byte characters (including Chinese characters): [^x00-xff]

Application: Calculate the length of a string (the length of a double-byte character is calculated 2. ASCII characters count as 1)

String.prototype.len=function(){return this.replace([^x00-xff]/g,"aa").length;}

Regular expression to match empty lines: n[s| ]*rRegular

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

Regular expression matching leading and trailing spaces: (^ s*)|(s*$)

Application: There is no trim function like vbscript in JavaScript. 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 the 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, but directly uses the split function to decompose it, it may be simpler. 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 matching of email addresses Expression: w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*

Regular expression matching URL: http: //([w-]+.)+[w-]+(/[w - ./?%&=]*)?Algorithm

program that uses regular expressions to remove repeated characters in a string:

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

uses regular expressions to extract the file name from the URL address. The following result is page1

s=" http://www.9499.net/page1.htm "
s=s.replace(/(.*/)([^.]+).*/ig,"")
alert(s)

uses regular expressions to limit the input content of the text box in the web form:

Use regular expressions to limit only Chinese input:

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

Use regular expressions to limit only input Full-width characters:

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

Use regular expressions to limit input to numbers:

onkeyup="value=value.replace(/[^d]/g,'') "onbeforepaste ="clipboardData.setData('text',clipboardData.getData('text').replace(/[^d]/g,''))"

Use regular expressions to limit input to numbers and English:

onkeyup=" value=value.replace(/[W]/g,'') "onbeforepaste="clipboardData.setData('text',clipboardData.getData('text').replace(/[^d]/g,' '))"