Should I use GraphQL for fine-grained validation?

For example, I want to validate an email field.

Should I define my own email scalar type or just use GraphQLString and validate the value in the resolve function?

new GraphQLScalarType({
  name: 'Email',
  coerce: value => '' + value,
  coerceLiteral: ast => ast.kind === Kind.STRING && ast.value.match(/somePattern/) ?
    ast.value :
    null
});

Similar question for checking the length of a string. If I have a field that map to a VARCHAR(100) in a MySQL database, should I create a specific scalar that check for a valid length? Not sure if it’s belongs to GraphQL… or if it is a good practise.

Any thoughts?

Thanks

[koistya]

Example: Input validation and user-friendly error messages in GraphQL mutations on Medium.com

[leebyron]

Thanks for the note, I’ll add a comment in code to explain what’s going on here.

+value calls ToNumber internally.

num === num is a cheap way to identify if num is the value NaN. NaN is not equal to anything, including itself. Everything else will be a number.