GraphQL UUIDv4 Custom Scalar Type

uuidv4_type.js

const validator = require('validator');

const UUIDv4Error = 'Invalid UUIDv4';

const validateUUIDv4 = value => validator.isUUID(value, 4);

exports.UUIDv4 = new GraphQLScalarType({
    name: 'UUIDv4',

    description: 'Valid UUIDv4',

    serialize(value) { // result coercion
        if (validateUUIDv4(value)) {
            return value;
        }

        throw new Error(UUIDv4Error);
    },

    parseValue(value) { // input coercion
        if (validateUUIDv4(value)) {
            return value;
        }

        throw new Error(UUIDv4Error);
    },

    parseLiteral(ast) { // input coercion
        if (validateUUIDv4(ast.value)) {
            return ast.value;
        }

        throw new Error(UUIDv4Error);
    }
});