Javascript 为什么在MongoDB游标上使用.sort（）会导致这个奇怪的错误？

我有以下JavaScript：

var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017/forex-backtesting';

MongoClient.connect(url, function(err, db) {
    var cursor = db.collection('datapoints').find({}).sort({timestamp: 1});

    function next(error, dataPoint) {
        if (!dataPoint) {
            return;
        }

        console.log(dataPoint.data.timestamp);
        cursor.nextObject(next);
    }

    cursor.nextObject(next);
});

我的数据点集合中有6000多个文档。当我运行此操作时，会出现以下错误：

/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/lib/utils.js:98
    process.nextTick(function() { throw err; });
                                        ^
TypeError: Cannot read property 'timestamp' of undefined
    at next (/Users/chad/development/desktop/forex-backtesting/mongodb.js:13:35)
    at handleCallback (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/lib/utils.js:96:12)
    at /Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/lib/cursor.js:666:5
    at handleCallback (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:249:5)
    at nextFunction (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:755:5)
    at /Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:723:9
    at queryCallback (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/wireprotocol/2_6_support.js:105:5)
    at Callbacks.emit (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:95:3)
    at null.messageHandler (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:243:23)
    at Socket.<anonymous> (/Users/chad/development/desktop/forex-backtesting/node_modules/mongodb/node_modules/mongodb-core/lib/connection/connection.js:262:22)

使用此签名

var cursor = db.collection('datapoints').find({}).sort([['timestamp', 1]]);

---

sort不返回任何东西，它只是对数组本身进行排序。但是为什么我在使用.sort.Please发布匿名化的708文档时能够迭代708次。它发布在原始问题中。不幸的是，使用此语法时问题仍然存在。现在看起来像：var stream=DataPoint.find{symbol:self.symbol}，null，{timeout:true}.sort['timestamp'，1]].stream；。

var cursor = db.collection('datapoints').find({}).sort([['timestamp', 1]]);