SchemaType.prototype.transform()

Parameters

• fn «Function»

Returns:

• «SchemaType» this

Defines a custom function for transforming this path when converting a document to JSON.

Mongoose calls this function with one parameter: the current value of the path. Mongoose then uses the return value in the JSON output.

Example:

const schema = new Schema({
  date: { type: Date, transform: v => v.getFullYear() }
});
const Model = mongoose.model('Test', schema);
await Model.create({ date: new Date('2016-06-01') });
const doc = await Model.findOne();
doc.date instanceof Date; // true
doc.toJSON().date; // 2016 as a number
JSON.stringify(doc); // '{"_id":...,"date":2016}'