想去看看，函数如何统一处理 callback 和 promise 的办法，然后去找找了 leancloud 和 parse 的代码看看，乖乖，这两个真像。

• leancloud-js-sdk query.js

  get: function(objectId, options) {
      if(!objectId) {
        var errorObject = new AV.Error(AV.Error.OBJECT_NOT_FOUND,
                                          "Object not found.");
        throw errorObject;
      }

      var self = this;
      self.equalTo('objectId', objectId);

      return self.first().then(function(response) {
        if (!_.isEmpty(response)) {
          return response;
        }

        var errorObject = new AV.Error(AV.Error.OBJECT_NOT_FOUND,
                                          "Object not found.");
        return AV.Promise.error(errorObject);

      })._thenRunCallbacks(options, null);
    },

• parse-js-sdk ParseQuery.js

get(objectId: string, options?: FullOptions): ParsePromise {
    this.equalTo('objectId', objectId);

    var firstOptions = {};
    if (options && options.hasOwnProperty('useMasterKey')) {
      firstOptions.useMasterKey = options.useMasterKey;
    }
    if (options && options.hasOwnProperty('sessionToken')) {
      firstOptions.sessionToken = options.sessionToken;
    }

    return this.first(firstOptions).then((response) => {
      if (response) {
        return response;
      }

      var errorObject = new ParseError(
        ParseError.OBJECT_NOT_FOUND,
        'Object not found.'
      );
      return ParsePromise.error(errorObject);
    })._thenRunCallbacks(options, null);
  }

最后一句都是：_thenRunCallbacks(options, null);心有灵犀一点通。

求大神科普 Parse中的代码：get(objectId: string, options?: FullOptions): ParsePromise这句中，还带有类型？