javascript callback

var sortJson = function(obj, callback) {
  var endValue, item, key, keyArray, keyArray2, o, _i, _len;
  endValue = {};
  keyArray = [];
  keyArray2 = [];
  for (key in obj) {
    o = {};
    o[key] = obj[key];
    keyArray.push(key);
  }
  keyArray2 = keyArray.sort();
  for (_i = 0, _len = keyArray2.length; _i < _len; _i++) {
    item = keyArray2[_i];
    endValue[item] = obj[item];
  }
  return typeof callback === "function" ? callback(endValue) : void 0;
};

var obj ={"2018-01-04":"1月4号数据","2018-01-01":"1月1号数据","2018-01-02":"1月2号数据","2018-01-03":"1月3号数据"};
sortJson(obj,function(data){console.log(data);});