dot.ts

export type DeepDotKey<T> = {
  [P in keyof T]: DeepDotKey<T[P]>;
} & (() => string);

/**
 * Type safe string builder deep dot notation
 * 
 * @example
 *   interface Foo {
 *     dictionary: { [key: string]: { value: number } | undefined };
 *     field: { prop: number };
 *     list: { node: string }[];
 *   }
 * 
 *   const _ = dot<Foo>();
 *   const key1 = _.field.prop(); // key1 === 'field.prop'
 *   const key2 = _.dictionary['hello'].value(); // key2 === 'dictionary.hello.value'
 *   const key3 = _.list[3].node(); // key3 === 'list.3.node'
 */
export function dot<T>(prev?: string): DeepDotKey<T> {
  return new Proxy(() => prev, {
    get: (_, next: string) => dot(prev ? `${prev}.${next}` : next),
  }) as DeepDotKey<T>;
}

playground.md

link