Promise是一种异步编程的代码书写方式，和Async模块一样，都能提高代码的可读性和可维护性。Async封装的比Promise要好，但是灵活性特别是彻底的去CallBack化会比Promise要差一点。下面直接贴下源代码，注释很详细：

（1）数据库连接文件：dbConfig

/**
 * Created by apple on 2014/12/29.
 */
var mongoskin = require(‘mongoskin‘);
var db = null;
var dbName = "yqbChat";

/**
 * @function
 * @param collectionName
 * @returns {SkinCollection|null|*}
 */
exports.getCollection = function (collectionName) {
    if (!db) {
        //连接本机mongodb ,使用帐号密码连接 mongoskin.db(‘username:[email protected]服务器ip/数据库名
        db = mongoskin.db(‘mongodb://127.0.0.1:27017/‘ + dbName + ‘?auto_reconnect=true&poolSize=3‘,
            {numberOfRetries: 1, retryMiliSeconds: 500, safe: true, native_parser: true},
            {socketOptions: {timeout: 5000}}
        );
    }
    return db.collection(collectionName);
};

/**
 * @function 关闭数据库
 */
exports.dbClose = function()
{
    if (!db) {
        db.close();
    }
};

(2)Model 层文件

/**
 * Created by apple on 2015/1/17.
 */
/** 聊天室数据结构
 *
 * //某两个用户对应的聊天室为一个集合，一个消息为一个文档
 * @{singleChatRoomID}
 *  @_id 信息编号
 *  @msgState 0-未读 1-已读 (int类型)
 *  @msgContent 消息内容
 *  @msgSend 消息发送者的user_id
 *  @create_time
 *
 */

//获取MongoDB的连接实例
var moment = require(‘moment‘);
var Q = require("q");

//存放聊天室配置集合
var singleChatRoomConfigInstance = null;

//当前时间点
var currentDateTime = moment().format("YYYY-M-D H:m:s");

/**
 * @function 根据singleChatRoomID在singleChatRoomConfig文档中搜索配置信息
 * @param singleChatRoomID 聊天室ＩＤ
 * @param callback　回调函数 如果为promise为空
 * @param promise 如果存在promise，则callback为空
 */
exports.findSingleChatRoomByID = function (data) {

    //根据singleChatRoomID搜索对应聊天室的配置，如果存在则返回聊天室配置，否则返回false
    if (singleChatRoomConfigInstance == null) {
        singleChatRoomConfigInstance = data.db.getCollection(‘singleChatRoomConfig‘);
    }

    var deferred = Q.defer();
    console.log("[SingleChatRoomConfig->findSingleChatRoomByID]:开始根据聊天室ID查找配置数据！");
    //查询
    singleChatRoomConfigInstance.findOne({singleChatRoomID: data.singleChatRoomID}, function (error, result) {

        if (typeof data.promise != undefined) {
            if (!error) {
                data.result = result;
                //console.log(data);
                deferred.resolve(data);
            } else {
                deferred.reject(error);
            }
        }
        else {
            callback(error, data);
        }
        //db.dbClose();
    });

    return deferred.promise;

};

/**
 * @function 在聊天室配置集合中插入新的集合
 * @param singleChatRoomID
 * @param user_id_1
 * @param user_id_2
 * @param callback
 * @param promise
 */
exports.insertSingleChatRoomByID = function (data) {
    //根据singleChatRoomID搜索对应聊天室的配置，如果存在则返回聊天室配置，否则返回false
    if (singleChatRoomConfigInstance == null) {
        singleChatRoomConfigInstance = data.db.getCollection(‘singleChatRoomConfig‘);
    }

    var deferred = Q.defer();
    console.log("[SingleChatRoomConfig->insertSingleChatRoomByID]:开始插入数据！");
    //console.log(data);
    singleChatRoomConfigInstance.insert(
        {
            singleChatRoomID: data.singleChatRoomID,
            users: [data.user_id_1, data.user_id_2],
            msgCount: 0,
            createTime: currentDateTime
        }, function (error, result) {
            if (typeof data.promise != undefined) {
                if (!error) {
                    data.result = result;
                    deferred.resolve(data);
                } else {
                    deferred.reject(error);
                }
                //db.dbClose();
            }
            else {
                callback(error, result);
                //db.dbClose();
            }

        }
    );
    return deferred.promise;

};

（3）Test文件

/**
 * Created by apple on 2015/1/17.
 */
var singleRoomConfigModel = require(‘../SingleRoomConfigModel‘);
var model = require(‘../Model‘);
var db = require(‘../db/dbConfig‘);
var Q = require("q");

/**
 * @function 测试在singleChatRoomConfig中查询是否存在某个聊天室的配置记录，不存在则创建
 * @param singleChatRoomID
 */
/**CallBack风格的函数*/
function testFindAndInsertByID_CALLBACK(singleChatRoomID) {
    //执行查询操作的回调函数
    this.findSingleChatRoomByIDCallBack = function (error, result) {

        console.dir("findSingleChatRoomByIDCallBack invoked!" + result);

        //如果结果不为空，则查询所有未读信息
        if (result != null) {

        }
        else
        //如果结果为空，则建立一条新的数据返回未读信息条数为空
        {
            singleRoomConfigModel.insertSingleChatRoomByID(singleChatRoomID, 1, 2, this.insertSingleChatRoomByIDCallBack);
        }

    };
    //执行插入操作的回调函数
    this.insertSingleChatRoomByIDCallBack = function (error, result) {

        if (error != null) {
            console.log(result);
        }
        else {
            console.error(error);
        }

    };
    singleRoomConfigModel.findSingleChatRoomByID(singleChatRoomID, this.findSingleChatRoomByIDCallBack);
}

/**Promise风格的函数*/
function testFindAndInsertByID_PROMISE(singleChatRoomID) {

    var data = {
        singleChatRoomID: singleChatRoomID,
        promise: true,
        db:db
    };

    singleRoomConfigModel.findSingleChatRoomByID(data).then(
        /**
         * @function 逻辑判断层，聊天室存在则返回聊天室信息，否则进入聊天室创建
         * @param result
         */
        function (data) {
            var deferred = Q.defer();
            if(data) {
                //console.log("聊天室存在，输出聊天室配置！");
                deferred.resolve(data);
            }
            else{
                //console.log("聊天室不存在，开始创建聊天室！");
                //继续设置下一层的promise调用
                deferred.reject(data);
            }
            return deferred.promise;
        }
        , model.errorHandler
    ).then(
        function(data){
            //console.log("获取到了聊天室配置！");
            var deferred = Q.defer();
            deferred.resolve(data);
            return deferred.promise;
        },
        singleRoomConfigModel.insertSingleChatRoomByID
    ).done(
        function(data){
            //console.log("testFindAndInsertByID_PROMISE-完毕");
            //console.log(data);
            data.db.dbClose()
        },
        model.errorHandler
    );

}

testFindAndInsertByID_PROMISE("1");