Mongoose document: Access a field that doesn't exist in the Schema

[fraction01]

Hi,

I want to access a field that doesn't exist in the schema, when I console.log the document I can see the field, also If I use document.get('myField') even without { strict: false }, but If I access using document.myField I get undefined which I find strange

const doc = await MyModel.findById(id);
console.log('doc', doc); // the field appears
console.log('myField', doc.get('myField')); // the field appears
console.log('myField 2', doc.myField) // undefined

[Sumit-Mayani]

This is expected behavior due to Mongoose's strict mode (enabled by default).

When you access doc.myField via dot notation, Mongoose only exposes paths defined in your schema. Paths not in the schema return undefined. However, doc.get("myField") uses an internal getter that reads directly from the underlying document data, bypassing schema restrictions — which is why it works.

Solutions:

1. Add the field to your schema (recommended):

const schema = new Schema({ myField: Schema.Types.Mixed });

2. Disable strict mode (allows any field to be stored and accessed):

const schema = new Schema({ ... }, { strict: false });

3. Convert to a plain object first:

const plain = doc.toObject();
console.log(plain.myField); // works

4. Use .lean() on the query (returns a plain JS object, not a Mongoose document — most performant for read-only use):

const doc = await MyModel.findById(id).lean();
console.log(doc.myField); // works

The lean() approach is the best choice if you only need to read data and don't need Mongoose document methods like .save().

[vkarpov15]

@Sumit-Mayani is right in general. strict is about which properties can be saved, with strict: false any additional properties in the document will get saved to the db. But Mongoose will always read whatever properties are in the database document, Mongoose just doesn't have a getter for properties that aren't in your schema.

[Sumit-Mayani]

Thanks for the clarification, @vkarpov15! To correct my solution #2: strict: false enables saving extra fields to the DB — it does not add dot-notation getters for non-schema paths. So doc.myField would still return undefined even with strict: false.

For reading a field that exists in DB but not in schema, the correct approaches are:

• doc.get('myField') — reads raw doc data directly
• doc.toObject() then access via dot notation
• .lean() on query — returns plain JS object, most performant