typescript中的keyPath提示

1type DotPrefix<T extends string> = T extends '' ? '' : `.${T}`;
2
3type KeyPaths<T> = (
4    T extends object ?
5      { [K in Exclude<keyof T, symbol>]: `${K}${DotPrefix<KeyPaths<T[K]>> | ''}` }[Exclude<keyof T, symbol>] :
6      ''
7  ) extends infer D ?
8    Extract<D, string> :
9    never;
10
11const obj = {
12  a: 1,
13  b: {
14    c: true,
15    d: {
16      e: 'string',
17    },
18  },
19};
20function getValue(keyPath: KeyPaths<typeof obj>) {
21
22}
23getValue('b.d.e');
24getValue('b.d');
25getValue('a');