Validation

enforce business logic
preserve data integrity
avert malicious inputs

Directives

Ex: graphql-constraint-directive (featured in Apollo Blog)

Pros

GraphQL centric and versatile

Cons

Does not allow for @constraint on query args
No compat with apollo-server v2, quirks in v1

Resolvers

Ex: validating args.id for an ObjectID

Pros

Simple and intuitive

Cons

Too repetitive, not DRY
Clutters up, doesn't scale

Utils

Ex: pure funcs using validator.js

Pros

Simple enough, composable, can scale

Cons

Reinventing the wheel
Code to maintain

ODM/ORM

Ex: built-in validators in Mongoose

Pros

Common checks
Extensible
- define custom validation logic
- customize error messages

Cons

Too many gotchas, e.g.
- unique is not a validator, but a unique index
- update* validators are off by default
- many pre/post hooks don't fire for update*
Hard to validate a subset of fields
- e.g. findById then save will validate all fields
Models grow out of size

Object Schema

Ex:

ajv
schm
joi
- yup for browsers (used in formik)

Pros

Very expressive & readable
DRY, doesn't clutter up
Extensible & customizable
- custom validators, plugins, messages

Cons

Cryptic error messages (though customizable)