Some conversions of some commonly used regular expression characters in PHP_PHP tutorial

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

Application: Calculate the length of a string (a double-byte character is counted as 2, ASCII characters are counted as 1)

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

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

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

Regular expression to match 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 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 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 the input of only 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 the input of numbers only:

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 only:

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

http://www.bkjia.com/PHPjc/319352.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/319352.htmlTechArticleMatch double-byte characters (including Chinese characters): [^x00-xff] Application: Calculate the string Length (the length of a double-byte character is counted as 2, and the length of an ASCII character is counted as 1) String.prototype.len=function(){ret...