Express 子文档mongoose返回[object]

以[object]而不是值返回的子文档

我正在尝试从子文档中检索值。但是子文档作为[object]返回。我已经读了一些关于这方面的文章，并尝试了下面的代码解决方案，它仍然给我[object]而不是值

MongoDB文档示例：

{
    "_id" : ObjectId("5d6b764d95d5d00337ce4a61"),
    "city" : "Berlin",
    "courses" : [ 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }
    ]
}

// Define collection and schema for todo item
var course = new mongoose.Schema(
    {
        course_date_start: String,
        course_date_end: String,
        course_price: String,
        course_trainer: String,
        date_added: String,
    }
);

var courses = new mongoose.Schema(
    {
        _id: {
            type: mongoose.Schema.Types.ObjectId,
            required: true
        },
        city: {
            type: String
        },
        courses: [course],
        child: course
    },
    {
        collection: 'courses'
    }
);

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [ [Object], [Object], [Object], [Object], [Object], [Object] ]
  }

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [{
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }]
  }

我的路线为“/课程”

我已经为我的型号尝试了以下代码：

{
    "_id" : ObjectId("5d6b764d95d5d00337ce4a61"),
    "city" : "Berlin",
    "courses" : [ 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }
    ]
}

// Define collection and schema for todo item
var course = new mongoose.Schema(
    {
        course_date_start: String,
        course_date_end: String,
        course_price: String,
        course_trainer: String,
        date_added: String,
    }
);

var courses = new mongoose.Schema(
    {
        _id: {
            type: mongoose.Schema.Types.ObjectId,
            required: true
        },
        city: {
            type: String
        },
        courses: [course],
        child: course
    },
    {
        collection: 'courses'
    }
);

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [ [Object], [Object], [Object], [Object], [Object], [Object] ]
  }

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [{
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }]
  }

以及以下

var courses = new mongoose.Schema(
    {
        _id: {
            type: mongoose.Schema.Types.ObjectId,
            required: true
        },
        city: {
            type: String
        },
        courses: [{
            course_date_start: String,
            course_date_end: String,
            course_price: String,
            course_trainer: String,
            date_added: String,
        }]
    },
    {
        collection: 'courses'
    }
);

按现在的方式点击端点localhost/courses时，我的“错误”控制台日志输出：

{
    "_id" : ObjectId("5d6b764d95d5d00337ce4a61"),
    "city" : "Berlin",
    "courses" : [ 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }
    ]
}

// Define collection and schema for todo item
var course = new mongoose.Schema(
    {
        course_date_start: String,
        course_date_end: String,
        course_price: String,
        course_trainer: String,
        date_added: String,
    }
);

var courses = new mongoose.Schema(
    {
        _id: {
            type: mongoose.Schema.Types.ObjectId,
            required: true
        },
        city: {
            type: String
        },
        courses: [course],
        child: course
    },
    {
        collection: 'courses'
    }
);

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [ [Object], [Object], [Object], [Object], [Object], [Object] ]
  }

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [{
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }]
  }

预期的控制台日志输出：

{
    "_id" : ObjectId("5d6b764d95d5d00337ce4a61"),
    "city" : "Berlin",
    "courses" : [ 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }
    ]
}

// Define collection and schema for todo item
var course = new mongoose.Schema(
    {
        course_date_start: String,
        course_date_end: String,
        course_price: String,
        course_trainer: String,
        date_added: String,
    }
);

var courses = new mongoose.Schema(
    {
        _id: {
            type: mongoose.Schema.Types.ObjectId,
            required: true
        },
        city: {
            type: String
        },
        courses: [course],
        child: course
    },
    {
        collection: 'courses'
    }
);

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [ [Object], [Object], [Object], [Object], [Object], [Object] ]
  }

  {
    _id: 5d6b764d95d5d00337ce4a61,
    city: 'Berlin',
    courses: [{
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }, 
        {
            "course_date_start" : "2019-09-26",
            "course_date_end" : "2019-09-27",
            "course_price" : "2750",
            "course_trainer" : "Nux Company",
            "date_added" : "2019-09-01 07:42:05"
        }]
  }