Deep Value

deep-value.ts

type Path<T extends unknown[]> = T extends [
  infer A,
  infer B,
  infer C,
  infer D,
  infer E,
  infer F,
  infer G,
  infer H,
  infer I
]
  ? `${A & string}.${B & string}.${C & string}.${D & string}.${E & string}.${F &
      string}.${G & string}.${H & string}.${I & string}`
  : T;

export function deepValue<T extends object, P1 extends keyof T>(
  value: T,
  ...path: Path<[P1]>
): T[P1];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1]
>(value: T, ...path: Path<[P1, P2]>): T[P1][P2];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1],
  P3 extends keyof T[P1][P2]
>(value: T, ...path: Path<[P1, P2, P3]>): T[P1][P2][P3];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1],
  P3 extends keyof T[P1][P2],
  P4 extends keyof T[P1][P2][P3]
>(value: T, ...path: Path<[P1, P2, P3, P4]>): T[P1][P2][P3][P4];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1],
  P3 extends keyof T[P1][P2],
  P4 extends keyof T[P1][P2][P3],
  P5 extends keyof T[P1][P2][P3][P4]
>(value: T, ...path: Path<[P1, P2, P3, P4, P5]>): T[P1][P2][P3][P4][P5];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1],
  P3 extends keyof T[P1][P2],
  P4 extends keyof T[P1][P2][P3],
  P5 extends keyof T[P1][P2][P3][P4],
  P6 extends keyof T[P1][P2][P3][P4][P5]
>(value: T, ...path: Path<[P1, P2, P3, P4, P5, P6]>): T[P1][P2][P3][P4][P5][P6];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1],
  P3 extends keyof T[P1][P2],
  P4 extends keyof T[P1][P2][P3],
  P5 extends keyof T[P1][P2][P3][P4],
  P6 extends keyof T[P1][P2][P3][P4][P5],
  P7 extends keyof T[P1][P2][P3][P4][P5][P6]
>(
  value: T,
  ...path: Path<[P1, P2, P3, P4, P5, P6, P7]>
): T[P1][P2][P3][P4][P5][P6][P7];

export function deepValue<
  T extends object,
  P1 extends keyof T,
  P2 extends keyof T[P1],
  P3 extends keyof T[P1][P2],
  P4 extends keyof T[P1][P2][P3],
  P5 extends keyof T[P1][P2][P3][P4],
  P6 extends keyof T[P1][P2][P3][P4][P5],
  P7 extends keyof T[P1][P2][P3][P4][P5][P6],
  P8 extends keyof T[P1][P2][P3][P4][P5][P6][P7]
>(
  value: T,
  ...path: Path<[P1, P2, P3, P4, P5, P6, P7, P8]>
): T[P1][P2][P3][P4][P5][P6][P7][P8];

export function deepValue<T, P>(value: T, ...path: Path<P[]>) {
  for (const key of path.join().split('.')) value = value[key];
  return value;
}