CODEWITHSUNDEEP
node.jsmongodbmongoose
wintzer
wintzer

Reputation: 911

Why does Mongoose add blank arrays?

I am trying to start using Mongoose as an ODM for MongoDB with my node.js application. I have noticed that when I design a schema with an embedded document that if I don't add a value to it, it store a blank array "[]" in Mongo. Why is this? I am trying to store historical changes to records and a blank array would mean that that change deleted the value. Here is a sample schema.

schema.Client = new mongoose.Schema({
    name:{type:String, required:true},
    products:[{
        name:{type:String, index:true},
        startDate:Date,
        endDate:Date
    }],
    subdomain:{type:String, index:{unique:true}},
})

Here is the resulting document when I save a document with just name and subdomain.

{
    "name": "Smith Company",
    "products": [],
    "subdomain": "smith"
}

Why did it add products with a blank array by default and how can I stop it?

Upvotes: 38

Views: 24572

Answers (6)

Owl
Owl

Reputation: 31

This worked for me. the object is not saved at all if you don't send it. this was my issue an empty object with empty sub arrays so my code was recognizing it in a forEach.

This one is referencing another schema as a subschema.

runtimeParams:{ type:[param], required:false, default:()=> undefined }, This one is a plain string array.

stages:{
    type:[String],
    required:false,
    default:()=> undefined
},

Upvotes: 0

Muslem Omar
Muslem Omar

Reputation: 1141

By default the array has [] value. you can overwrite that : 

var UserSchema = new Schema({
  followers : {
    type: [String],
    default: undefined
  }
})

Upvotes: 16

Angelo Chen
Angelo Chen

Reputation: 551

You can workaround by define the schema like below:

products: {
  type: [{
    name:String,
    startDate:Date,
    endDate:Date
  }],
  default: undefined
}

Upvotes: 50

jasoncrawford
jasoncrawford

Reputation: 2763

This seems to be by design, but there is a workaround here using a 'pre' handler to remove the default empty array: https://github.com/LearnBoost/mongoose/issues/1335

This only worked for me when I set the field to null, though. If I set it to undefined as in the sample code, the empty array seems to come back.

Upvotes: 3

jwchang
jwchang

Reputation: 10864

Blank array gives you convenient way to add or remove elements from your Model.

$push $addToSet $pull in update would help you to manage your array elements.

If you don't have a blank array then you cannot push elements to null

But it is possible in blank array.

Upvotes: 25

Menztrual
Menztrual

Reputation: 41607

Because in your schema you are defining products to be an array of objects. You would need to try something like:

products: {
        name:{type:String, index:true},
        startDate:Date,
        endDate:Date
    },

This will store an empty object instead of an array.

Upvotes: 0

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