javascript - “TypeError: Cannot read property '的' of undefined”。这个在议程.js中是什么意思？

这是堆栈跟踪:当我在项目中运行server.js文件时，就会发生这种情况。另外，我在网上找不到任何解释。有人可以帮忙解决这个错误吗？

E:\users\ashane\documents\visual studio 2015\Projects\ShowTracker\ShowTracker\node_modules\agenda\lib\agenda.js:341
  if ( this._mdb.s.topology.connections().length === 0 ) {                ^

TypeError: Cannot read property 's' of undefined
    at Agenda._findAndLockNextJob (E:\users\ashane\documents\visual studio 2015\Projects\ShowTracker\ShowTracker\node_modules\agenda\lib\agenda.js:341:17) at jobQueueFilling (E:\users\ashane\documents\visual studio 2015\Projects\ShowTracker\ShowTracker\node_modules\agenda\lib\agenda.js:420:10) at processJobs (E:\users\ashane\documents\visual studio 2015\Projects\ShowTracker\ShowTracker\node_modules\agenda\lib\agenda.js:404:7)

    at doNTCallback0 (node.js:417:9)
    at process._tickCallback (node.js:346:13)
    at Function.Module.runMain (module.js:469:11)
    at startup (node.js:134:18)
    at node.js:961:3

这些是唯一使用议程和“s”

var mongoConnectionString = "mongodb://127.0.0.1/agenda";
var agenda = require('agenda')({ db: { address: mongoConnectionString } });
var sugar = require('sugar');
var nodemailer = require('nodemailer');

// define an agenda job called send email alert.

agenda.define('send email alert', function (job, done) {
    // what should happen when send email alert job is dispatched.
    // When this job runs, name of the show will be passed in as an optional data object.
    // Since we are not storing the entire user document in subscribers array (only references),
    // we have to use Mongoose’s populate method.
    Show.findOne({ name: job.attrs.data }).populate('subscribers').exec(function (err, show) {
        var emails = show.subscribers.map(function (user) {
            return user.email;
        });

        var upcomingEpisode = show.episodes.filter(function (episode) {
            return new Date(episode.firstAired) > new Date();
        })[0];

        var smtpTransport = nodemailer.createTransport('SMTP', {
            service: 'SendGrid',
            auth: { user: 'hslogin', pass: 'hspassword00' }
        });

        // standard Nodemailer boilerplate for sending emails.
        var mailOptions = {
            from: 'Fred Foo ✔ <[email protected]>',
            to: emails.join(','),
            subject: show.name + ' is starting soon!',
            text: show.name + ' starts in less than 2 hours on ' + show.network + '.\n\n' +
        'Episode ' + upcomingEpisode.episodeNumber + ' Overview\n\n' + upcomingEpisode.overview
        };

        smtpTransport.sendMail(mailOptions, function (error, response) {
            console.log('Message sent: ' + response.message);
            smtpTransport.close();
            done();
        });
    });
});

agenda.start();

agenda.on('start', function (job) {
    console.log("Job %s starting", job.attrs.name);
});

agenda.on('complete', function (job) {
    console.log("Job %s finished", job.attrs.name);
});

最佳答案

在议程.js中，在if ( this._mdb.s.topology.connections().length === 0 )行中，this._mdb是未定义的。

方法Agent.prototype.database将_mdb中返回的db对象分配给MongoClient.connect。所以我的猜测是连接操作失败。您确定您的连接字符串吗？