Node.js 检查多个Mongoose集合中特定字段的总和

我正在尝试为餐厅预订mongoose模式，但如果所有集合中的“人”值都超过50，我不希望人们能够预订

var reservationSchema = new mongoose.Schema ({
    people: Number,
    date: String,
    name: String,
    email: String
});

var Reservation = mongoose.model("Reservation", reservationSchema);

app.post('/reservation', (req, res) => {
    var people = parseFloat(req.body.people);
    var date = req.body.date;
    var name = req.body.name;
    var email = req.body.email;   

    var newReservation = {people: people, date: date, name: name, email: email};
    Reservation.create(newReservation, (err, newlyCreated) => {
        if(err) {
            console.log(err);
        } 
        else {
            res.redirect('/');
        }
    })
});

---

当您将来自人员的所有值相加时，如何筛选所有集合以查找数字？

您需要使用聚合管道来计算人员的总数。如果计数小于50，则创建新预订，否则显示一些消息

为此，您可以使用

statics

方法

var reservationSchema = new mongoose.Schema ({
    people: Number,
    date: String,
    name: String,
    email: String
});


reservationSchema.statics = {
    createIfSpaceAvailable : function(newReservation, done){
        var Reservation = this;
        Reservation.aggregate([
        {
         $group:{
             _id: null,
             noOfPeople: { $sum: "$people"}
         }
        }], 
        function(err, result){
        if(err){
            return done(err);
        }
        else if(result[0].noOfPeople > 50){
            // do something
        }
        else{
            Reservation.create(newReservation, (err, newlyCreated) => {
                if(err) {
                     return done(err);
                } 
                else {
                     return done();
                }
            })
        }
    })
   }
};
var Reservation = mongoose.model("Reservation", reservationSchema);

app.post('/reservation', (req, res) => {
    var people = parseFloat(req.body.people);
    var date = req.body.date;
    var name = req.body.name;
    var email = req.body.email;   

    var newReservation = {people: people, date: date, name: name, email: email};
    Reservation.createIfSpaceAvailable(newReservation, (err, newlyCreated) => {
        if(err) {
            console.log(err);
        } 
        else {
            res.redirect('/');
        }
    })
});

---

您可以使用聚合管道-请参阅：

特别是

$sum

运算符：

顺便说一下，由于节点v4.x没有写入：

var newReservation = {people: people, date: date, name: name, email: email};

您可以使用较短的语法：

var newReservation = {people, date, name, email};

见：

---

为什么

\u id:null

？@TalhaAwan感谢您的回答，但我得到了TypeError:无法读取未定义的属性'noOfPeople'。@JKshort，

console.log（result）

以检查数据是如何返回的。我不确定它是否是

result.noOfPeople

或

result[0]。noOfPeople

@TalhaAwan这是result[0]。noOfPeople，我没有在if语句中添加任何内容，可能是导致问题的原因，但它现在起作用了。感谢所有这一切都没有错，功能正在工作，但我需要在数据库中至少有一个集合。如果为空，则显示错误