js

1.扩展string类型，添加一个trim方法取出字符串两边空白

原理：prototype属性

<script type="text/javascript">

       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,"");
}

       var a = "sdf";
       a.trim();
   </script>