js substring从右边获取指定长度字符串(示例代码)

/* 

   Get the rightmost substring, of the specified length, 

   from a String object. 

*/  

String.prototype.right = function (length_)  

{  

        var _from = this.length - length_;  

        if (_from < 0) _from = 0;  

        return this.substring(this.length - length_, this.length);  

};