MongoDB: Removing an Object from an Array

In MongoDB, you can remove an object from an array embedded in a document using the $pull operator. If you wish to remove a specific object from an array, you need to provide a query that matches the exact object.

Consider the following document:

{
   _id: 5150a1199fac0e6910000002,
   name: 'some name',
   items: [{
      id: 23,
      name: 'item name 23'
   },{
      id: 24,
      name: 'item name 24'
   }]
}

To remove the item with id: 23 from the items array, use the following command:

db.mycollection.update(
    { '_id': ObjectId("5150a1199fac0e6910000002") }, 
    { $pull: { items: { id: 23 } } },
    false, // Upsert
    true, // Multi
);

This command updates the document by removing the item from the array. The query specifies the document using the _id field, and the $pull operator targets the items array. Within the $pull operation, you can specify a query to match the object to be removed. In this case, we match the object with id: 23.

Mongoose/Node.js Implementation

In Mongoose, you can remove an object from an array using the pull() method:

const Model = mongoose.model('Model', new mongoose.Schema({
  items: [{
    id: Number,
    name: String
  }]
}));

Model.update(
  { '_id': '5150a1199fac0e6910000002' },
  { $pull: { items: { id: 23 } } },
  { multi: true }, // Update all matching documents
  (err, result) => { if (!err) console.log(result); }
);

This code will remove the item with id: 23 from the items array of all documents that match the specified _id.