javascript trim、left、right等函数，兼容IE,FireFox

《style》
body,td,div{font:menu}
《/style》
《script》
//code by windy_sk , seasonx@163.net
//测字符串实际长度
String.prototype.Tlength = function(){var arr=this.match(/[^\x00-\xff]/ig);return this.length+(arr==null?0:arr.length);}

//字符串左取
String.prototype.left = function(num,mode){if(!/\d+/.test(num))return(this);var str = this.substr(0,num);if(!mode) return str;var n = str.Tlength() - str.length;num = num - parseInt(n/2);return this.substr(0,num);}

//字符串右取
String.prototype.right = function(num,mode){if(!/\d+/.test(num))return(this);var str = this.substr(this.length-num);if(!mode) return str;var n = str.Tlength() - str.length;num = num - parseInt(n/2);return this.substr(this.length-num);}

//字符串包含
String.prototype.GetCount = function(str,mode){return eval("this.match(/("+str+")/g"+(mode?"i":"")+").length");}

//字符串去除两端空字符
String.prototype.Trim=function(){return this.replace(/(^\s*)|(\s*$)/g,"");}
String.prototype.Ltrim = function(){return this.replace(/(^\s*)/g, "");}
String.prototype.Rtrim = function(){return this.replace(/(\s*$)/g, "");}

document.write("'aa啦啦aa'.Tlength() = " + "aa啦啦aa".Tlength());
document.write("《br》");
document.write("'aabbcc'.Tlength() = " + "aabbcc".Tlength());
document.write("《br》");
document.write("'aa啦啦aa'.left(4) = " + "aa啦啦aa".left(4));
document.write("《br》");
document.write("'aa啦啦aa'.left(4,true) = " + "aa啦啦aa".left(4,true));
document.write("《br》");
document.write("'aa啦啦aa'.right(4) = " + "aa啦啦aa".right(4));
document.write("《br》");
document.write("'aa啦啦aa'.right(4,true) = " + "aa啦啦aa".right(4,true));
document.write("《br》");
document.write("'abAcae'.GetCount('a') = " + "abAcae".GetCount("a"));
document.write("《br》");
document.write("'abAcae'.GetCount('a',true) = " + "abAcae".GetCount("a",true));
document.write("《br》");
document.write("'  abc  de    '.Ltrim() = " + "  abc  de    ".Ltrim());
document.write("《br》");
document.write("'  abc  de    '.Rtrim() = " + "  abc  de    ".Rtrim());
document.write("《br》");
document.write("'  abc  de    '.Trim() = " + "  abc  de    ".Trim());
《/script》