如何在另一个集合中使用变量

Question

我想显示'会议'收集会议，其主机电子邮件（来自'用户'集合）包含短语'agu'。这里会议主持人的电子邮件是从用户集合中调用的：

var host = meetings.host

db.collection('users').findOne({'_id': new ObjectId(host)}, function(err, doc) {
    var emails = [];
    if (doc.emails) {
        doc.emails.forEach(function(e) {
            emails.push(e.email + (e.primary ? '(P)' : ''));
        });
    }
    var email = emails.join(', ');

以下是使用包含短语“fall”的DisplayValue（title）的meetings集合属性进行代码查找的示例：

function findMeetings(db, callback) {
    var cursor = db.collection('meetings').find({
      'name.displayValue': {'$regex': 'fall', '$options': 'i' }
    });
    cursor.count(function(err, count) {
        console.log('count: ' + count);
        var cnt = 0;
        cursor.each(function(err, doc) {
            assert.equal(err, null);
            if (doc != null) {
                findNumberOfNotesByMeeting(db, doc, function() {
                    cnt++;
                    if (cnt >= count) { callback(); }
                });
            }
        });
    });
}

这是meetings.attendees属性的样子：

attendees: [{
    email: {type: String, default: ''},
    userId: {type: String, default: ''},
    isPresenter: {type: Boolean, default: false},
    invitationStatus: {type: String, default: ''},
    invitationResent: {type: Boolean, default: false}
}],

以下是用户架构的外观：

var userSchema = mongoose.Schema({
createdOn: { type: Number, default: 0},
updatedOn: { type: Number, default: 0},
emails: [{
    email: { type: String, default: ''},
    confirmed: { type: Boolean, default: false},
    primary: { type: Boolean, default: false}
}],
authentication: [{
    token: { type: String, default: ''},
    createdOn: { type: Number, default: 0}
}],
password: {
    salt: { type: String, default: ''},
    hash: { type: String, default: ''}
},
consecutiveFailedLoginAttempts: { type: Number, default: 0},
communicationOptions: {
    customerContact: { type: Boolean, default: false}
},
profileCompleted: { type: Boolean, default: false},
profile: {
    firstName: {
        searchValue: { type: String, default: ''},
        displayValue: { type: String, default: ''}
    },
    lastName: {
        searchValue: { type: String, default: ''},
        displayValue: { type: String, default: ''}
    },
    nickname: { type: String, default: ''},
    companyName: { type: String, default: ''},
    title: { type: String, default: ''},
    location: { type: String, default: ''},
    imageURL: { type: String, default: ''}
},
forgotPassword: {
    token: {type: String, default: ''},
    forgotOn: {type: Number, default: 0}
},
deleteAccount: {
    token: {type: String, default: ''},
    actionOn: {type: Number, default: 0},
    confirmedOn: {type: Number, default: 0}
},
anonymous: {type: Boolean, default: false}

}）;