Detailed explanation of commonly used regular expression character conversion in PHP

For some front-end regular operations, you can modify it to become PHP's

to match double-byte characters (including Chinese characters): [^\x00-\xff]

Application: Calculate the length of string (the length of a double-byte character counts as 2, and the length of an ASCII character counts as 1)

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

Matching the regular expression# for empty lines ##： \n[\s| ]*\r
Regular expression matching HTML tags: /db05f8e866f47612e82f5cb19e67888c.*0e1c620fd1f13d4254a0bb23aec420ea|26a4900594fb36752f3c6c1685615206/

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

Application: Not available in
javascript For a trim function like vbscript, we can use this expression to implement 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 //匹配IP地址的正则表达式  
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("IP值是："+(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) //结果为：abcefgi

Using regular expressions to extract characters from a URL A javascript program that extracts the file name from the address. The following result is page1

s="http://www.php.cn/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 Enter Chinese:


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 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 only:

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

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