ndoejs+mongodb 开发2：去重

/**auother : zhz * 去重复查询condition:查询条件，field:去重复列，查询结果（注意：返回结果只有一列，就是field列，也是选择的去重复选项列） */HelperMongo.prototype.mgDistict = function(collectionName, condition,fields,callback) {    var self = this;    var reqId = _reqId++;    _log(reqId,"开始查找数量... "+collectionName+","+JSON.stringify(condition));    if(fields == null){        return;    }    var field = fields['field'];    function process(callback) {        _getCollection(self, collectionName, function (collection) {            collection.distinct(field,condition,function (error, rst) {                if (error) {                    global.err(collectionName + " : " + JSON.stringify(error));                    return;                }                _log(reqId, "查找成功--> " + JSON.stringify(rst));                if(callback != undefined) callback(rst);            });        });    }    return _judgePromise(process,callback);};