I have a strange but simple issue with array in javascript and node js?

Question

very simple question that waste my time for several hours: I just try to push data to an array which exists in my schema but when I use the .push I got error that 'can not read property push of undefined' here is my very simple code:

var mongoose = require("mongoose");
mongoose.connect("mongodb://localhost/new_try1");

var productSchema = new mongoose.Schema({
    number: Number,
    name: String
});

var Product = mongoose.model("Product", productSchema);

var orderSchema = new mongoose.Schema({
    number: Number,
    name: String,
    products: [productSchema]
});

var Order = mongoose.model("Order", orderSchema);

var newOrder = new Order({
    number: "123",
    name: "jane"
});


newOrder.save(function (err, order) {
    if (err) {
        console.log(err);
    } else {
        console.log(order);
    }
});
Order.find({
    name: 'jane'
}, function (err, order) {
    if (err) {
        console.log(err)
    } else {
        console.log(order);// I can see the products array in cmd
        console.log(order.products);// I got undefined here!!!!!????
        order.products.push({// here I got error can not read of un....
            number:456,
            name:'carret'
        });
        order.save(function(err,found){
            if (err){
            console.log(err);   
            }else{
                console.log(found);
            }
        })
    }
});

when run the server I got this in cmd for order:

[{_id:357636shgs65dh5sd4h65d,
number:'123',
name:'jane',
__v:0,
products:[] }]

now why order.product is undefined when I can see it here?

your output suggests order is an array, so you need to use order[0].products maybe!? — xander
– xander, Commented Apr 21, 2017 at 11:28
I am sure the syntax is right because I already use it in another project but the strange is that the same syntax doesn't work in another project!? — milad fahimi
– milad fahimi, Commented Apr 21, 2017 at 11:33

Jonas Wilms · Accepted Answer · 2017-04-21 11:39:13Z

1

To make it simple, it looks like order is this:

var order=[
       {_id:357636shgs65dh5sd4h65d,
           number:'123',
           name:'jane',
           __v:0,
           products:[] 
        }];

As you can see its an Array not an Object. So you first need to get the Object of the Array:

order //the array
  [0] //the object
  .products //the product array
  .push()//should work now

collection.find returns a cursor to a collection, wich needs to be iterated (= Arraylike) so you may want to use collection.findOne wich returns just one element, making your code work.

https://docs.mongodb.com/v3.2/reference/method/db.collection.find/ https://docs.mongodb.com/v3.2/reference/method/db.collection.findOne/

Order.findOne({
  name: 'jane'
}, function (err, order) {
   order.push("data");
});

edited Apr 21, 2017 at 11:39

answered Apr 21, 2017 at 11:33

Jonas Wilms

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2 Comments

milad fahimi Over a year ago

with order[0].products.push i didn't get any error but nothing added to my array!!

milad fahimi Over a year ago

thank you dear Jonas using .findOne instead of .find solve my problem

Aidan Gee · Accepted Answer · 2017-04-21 11:33:42Z

0

Looks like your order is an array. So somethiing like this should work:

Order.find({
    name: 'jane'
}, function (err, order) {
    if (err) {
        console.log(err)
    } else {
        console.log(order);// I can see the products
        console.log(order[0].products);
        order[0].products.push({
            number:456,
            name:'carret'
        });
        order.save(function(err,found){
            if (err){
            console.log(err);   
            }else{
                console.log(found);
            }
        })
    }
});

Note: Im not sure on your use case. But it looks like you could retreive multiple orders back from your db so you'll probably want to loop over the orders returned for processing as well

answered Apr 21, 2017 at 11:33

Aidan Gee

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1 Comment

milad fahimi Over a year ago

with order[0].products.push i didn't get any error but nothing added to my array!!

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