Scalar Type Definition

The leaf values of any request and input values to arguments are Scalars (or Enums) and are defined with a name and a series of functions used to parse input from ast or variables and to ensure validity.

If a type's serialize function does not return a value (i.e. it returns undefined) then an error will be raised and a null value will be returned in the response. If the serialize function returns null, then no error will be included in the response.

Example:

const OddType = new GraphQLScalarType({
  name: 'Odd',
  serialize(value) {
    if (value % 2 === 1) {
      return value;
    }
  }
});