JavaScript中为String对象添加trim()方法

<script language=Javascript>  //自己动手为string添加Trim
    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 str = "  SSSSSSSSS    ";
    alert(str.Trim());
    alert(str.Ltrim());
    alert(str.Rtrim());
</script>