How to Make Mongoose Not Insert Empty Array or Object Fields into a Document

How to make Mongoose not insert empty array or object fields into a document

you can do it easily skip the array field and array of object field.. This will let you skip saving empty array in new documents.but you have to use pre hook for this .

var brandSchema = new Schema({
    name : {type:String},
    email:String,
    check:[]
})

brandSchema.pre('save', function (next) {
  if (this.isNew && 0 === this.check.length) {
    this.check = undefined;                                                                                                                                   
  }
  next();
})

when new document is inserted in your schema you have to use this middlware.this works fine so try this.
this is the response when we want to insert any document

"data": {
    "__v": 0,
    "name": "testing",
    "email": "testing@gmail.com",
    "_id": "5915b018e292833edda8837f"
  }

so i have send only email and name but check(array) field is skipped(Not send any value).

Mongoose schema creates empty array field

When you are saving the document, mongoose look at the schema of the related collection.

It takes all fields you are giving to it and set the values up. It also create default values for the fields you did provide nothing for.

That's the behavior of mongoose.

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In your case what can we do?

We gonna create two schema related to the same collection. One with the field cheese and one without. So when you gonna save a new document with the schema without cheese, it's not gonna get created.

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In practice, the collection will hold two different document type.

Here is a link about using multiple schema related to a single collection

mongoose - trying to save an array of documents, only empty array saved

The issue here is the body.modfulldata is an array and you simply can not create mongoose schema object like this, instead iterate the array and generate mongoose schema object and then insert them. Example:

const newmods = req.body.modfulldata.map(dataObj => {
                  return new ModulesModel(dataObj);
                });
await ModuleModel.insertMany(newmods);

Mongoose creating empty arrays?

Mongoose does do this on purpose, though I'm not sure why. If you set the properties that you don't want stored as undefined, they will be excluded from the document.

set field as empty for mongo object using mongoose

Sub-document in an array saves as an empty array item if no value is provided on document creation

You can specify empty array as the default value for notes. And you don't need to return a function for the SubDocumentSchema. Try the below edited code.

const SubDocumentSchema = new mongoose.Schema({
  content: {
    type: String,
    trim: true
  },
  date: {
    type: Date,
    default: Date.now
  }
})

const DocumentSchema = new mongoose.Schema({
  notes: {
    type: [SubDocumentSchema],
    default: []
  }
});

const Document = mongooseConnection.model('DocumentSchema', DocumentSchema)
const t = new Document()

t.save()

Mongoose specify optional array of objects

In mongoose an empty array is a default value for an array type. You can override it by using default field this way:

let optionsSchema = new mongoose.Schema(
    {
        answer: {
            type: String,
            required: true,
        },
        value: {
            type: Number,
            min: -10,
            max: 10,
            required: true,
        },
    },
    { _id: false });


const RootSchema = new Schema({
    options : {
        type: [optionsSchema],
        default: undefined
    }
})

Getting an empty array Mongoose

Specify the collection name when creating the schema, like:

const animalClassSchema = new mongoose.Schema({
  name: {type: String, required: true}
}, { collection: 'animalClass' });

By default, Mongoose pluralizes your collection name. This option allows you to override that behavior. More info in the docs:

https://mongoosejs.com/docs/guide.html#collection

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