Regular expressions in JavaScript

Remove extra spaces at the beginning and end of the string
/g is the full text search for all matching functions String.prototype.Trim(){return this.replace(/(^s*)|(s*$)/g, ""); }function String.prototype.LTrim(){return this.replace(/(^s*)/g, "");}

function String.prototype.RTrim(){return this.replace(/( s*$)/g, "");}

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

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

--------------- --------------------------------------------------
Application: There is no trim function in JavaScript like vbscript, we can use this expression to achieve it, as follows:

String.prototype.trim = function()
{
return this.replace(/(^s*)|(s *$)/g, "");
}
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(/(.*/){0,}([^.]+).*/ig,"$2")
alert(s)

##Use regular expressions to limit web pages Input content in the text box in the form:

---------------------------------------- -----------------------
Use regular expressions to limit input to Chinese only: 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 to only 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,'))"