sort Object attributes by function
and transfer them into array
@param  {Object} obj Object form from numric
@param  {Function} fn sort function
@return {Array} the sorted attirbutes array
function transObjectAttrIntoArray(obj) {
  var fn = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : function (a, b) {
    return +a - +b;
  };

  return _Object$keys(obj).sort(fn).reduce(function (order, key) {
    return order.concat(obj[key]);
  }, []);
}