How to convert a TypeScript built-in enum to a GraphQL enum

At Woovi we are GraphQL lovers, hence we develop many helpers around this tool to bring a good developer experience.

A helper that we developed is graphqlEnumBuilder, this helper allows us to convert a TypeScript built-in enum into a GraphQLEnum without difficulty. Thus, if you add a new value in your TypeScript enum, you don't need to edit your GraphQL enum, because it's generated from your TypeScript enum.

How it works

enum Gender {
  Male = 'Male',
  Female = 'Female',
}

const GenderEnumType = graphqlEnumBuilder(
  'GenderType',
  Gender,
);

When you call this GenderEnumType in some query or mutation as an argument and generate your schema file, note that the GenderEnumType is declared as an enum in the GraphQL notation.

Here is an example:

enum GenderType {
  Male
  Female
}

Code solution

import { GraphQLEnumType } from 'graphql';

type EnumObject = {
  [index: string]: string;
};

type EnumObjectResult = {
  [index: string]: {
    value: string;
  };
};
export const enumBuilderValues = <T = EnumObject>(
  constants: T,
): EnumObjectResult =>
  Object.keys(constants).reduce(
    (prev, curr) => ({
      ...prev,
      [curr]: {
        value: constants[curr],
      },
    }),
    {},
  );

export const graphqlEnumBuilder = <T = EnumObject>(name: string, values: T) =>
  new GraphQLEnumType({
    name,
    values: enumBuilderValues(values),
  });

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