Creates object with specyfied value types that can be extended by new key-value pairs.

map-builder.ts

const mapBuilder = <ValueType = never>() => {
  const addFactory = <Values extends Record<string, ValueType>>(values: Values) => ({
    add: <Key extends string>(key: Key, data: ValueType) =>
      addFactory({ ...values, [key]: data } as Record<keyof Values | Key, ValueType>),
    build: () => values,
  });

  return addFactory({});
};