Nested object to the do notations array

nested-object-dotted-notations.ts

type Primitive = string | number | boolean | bigint | symbol | undefined | null;

type PathImpl<T, K extends keyof T> = K extends string
  ? // eslint-disable-next-line @typescript-eslint/ban-types
  T[K] extends Function // Check if it's a function
  ? never // Exclude functions
  : T[K] extends Primitive // Check if it's a primitive value
  ? K // Include primitives directly
  : T[K] extends Record<string, any> // Check if it's an object to traverse
  ? T[K] extends ArrayLike<any>
  ? K | `${K}.${PathImpl<T[K], Exclude<keyof T[K], keyof any[]>>}` // Exclude array indices
  : K | `${K}.${PathImpl<T[K], keyof T[K]>}` // Traverse into the object
  : K
  : never;

type Path<T> = PathImpl<T, keyof T> | keyof T;
  
const obj = {
  a: {
    b: {
      c: 1,
      d: 'hello',
    },
  },
}

/**
 * Result:
 * 
 * type Test = Path<typeof obj>
 * 
 * type Test = "a" | "a.b" | "a.b.c" | "a.b.d"
 */