「重学TS 2.0 」TS 练习题第四十八题

[semlinker]

实现 ConsistsOnlyOf 工具类型，用于判断 LongString 字符串类型是否由 0 个或多个 Substring 字符串类型组成。具体的使用示例如下所示：

type ConsistsOnlyOf<LongString extends string, Substring extends string> = // 你的实现代码

type C0 = ConsistsOnlyOf<'aaa', 'a'> //=> true
type C1 = ConsistsOnlyOf<'ababab', 'ab'> //=> true
type C2 = ConsistsOnlyOf<'aBa', 'a'> //=> false
type C3 = ConsistsOnlyOf<'', 'a'> //=> true

请在下面评论你的答案

[zhaoxiongfei]

type ConsistsOnlyOf<LongString extends string, Substring extends string> = LongString extends ''
  ? true
  : LongString extends `${Substring}${infer B}`
    ? ConsistsOnlyOf<B, Substring>
    : false;

思路: 字符串匹配，利用 extends 、利用ts下支持的模板字符串语法，利用 infer 从开头一步步的去匹配，减治的思想。
随着递归的深入字符串愈来愈短，直至为空，注意空的话算匹配成功。

[zjxxxxxxxxx]

type ConsistsOnlyOf<
  LongString extends string,
  Substring extends string
> = LongString extends `${Substring}${infer R}`
  ? ConsistsOnlyOf<R, Substring>
  : LongString extends ""
  ? true
  : false;

[bill-lai]

type ConsistsOnlyOf<LongString extends string, Substring extends string> = 
  LongString extends '' 
    ? true
    : LongString extends `${Substring}${infer S}` 
      ? ConsistsOnlyOf<S, Substring>
      : false

[zhengyimeng]

type ConsistsOnlyOf<LongString extends string, Substring extends string> 
  = LongString extends `${Substring}${infer Others}`
    ? ConsistsOnlyOf<Others, Substring>
    : LongString extends '' ? true : false