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Dig

@RiccardoOdone•Suggest a tip•

Ensure at compile time that you are digging keys that exist in the object.

const dig = (
  key1: string,
  key2: string,
  obj: Record<string, Record<string, unknown>>
) => obj[key1][key2]

const obj = { a: { b: 1 }}

dig('a', 'b', obj) // 1
dig('z', 'x', obj) // ⛔️ BOOM

const dig = <
  Key1 extends string,
  Key2 extends string,
  Object extends Record<Key1, Record<Key2, unknown>>
>(key1: Key1, key2: Key2, obj: Object) =>
  obj[key1][key2]

const obj = { a: { b: 1 }}

dig('a', 'b', obj) // 1
dig('z', 'x', obj) // ✅ Does not compile
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