关于js 中对二维数组进行深拷贝的方法

 copyArr(obj) {
      var out = [],
        i = 0,
        len = obj.length;
      for (; i < len; i++) {
        if (obj[i] instanceof Array) {
          out[i] = this.copyArr(obj[i]);
        } else out[i] = obj[i];
      }
      return out;
    }