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