js substring从右边获取指定长度字符串(示例代码)

如下所示：
代码如下:
 /*

   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); 

};