Custom validators
In addition to the built-in validators, you can define custom validators. In custom validation, a validation function is passed along with the declaration. Defining a custom validator involves creating a specialized function within the schema’s field definition to ensure that the data inserted or updated meets specific criteria beyond the standard validation rules offered by Mongoose.
Mongoose Validation
Mongoose is a MongoDB object modeling and handling for a node.js environment. Mongoose Validation is essentially a customizable middleware that gets defined inside the SchemaType of Mongoose schema. It automatically fires off before a document is saved in the NoSQL DB. Validation can also be run manually using doc.validate(callback) or doc.validateSync() methods. Let’s understand more about this with the help of some examples.