25. TrimLeft、Trim、TrimRight

[astak16]

题目

题目链接：TrimLeft，Trim，TrimRight

实现 TrimLeft，满足以下要求

import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<TrimLeft<'str'>, 'str'>>,
  Expect<Equal<TrimLeft<' str'>, 'str'>>,
  Expect<Equal<TrimLeft<'     str'>, 'str'>>,
  Expect<Equal<TrimLeft<'     str     '>, 'str     '>>,
  Expect<Equal<TrimLeft<'   \n\t foo bar '>, 'foo bar '>>,
  Expect<Equal<TrimLeft<''>, ''>>,
  Expect<Equal<TrimLeft<' \n\t'>, ''>>,
]

答案

方法一

type Space = `${" " | "\t" | "\n"}`;
type TrimLeft<T extends string> = T extends `${Space}${infer R}`
  ? TrimLeft<R>
  : T;

方法二

type TrimLeft<T extends string> = T extends ` ${infer R}`
  ? TrimLeft<R>
  : T extends `\t${infer R}`
  ? TrimLeft<R>
  : T extends `\n${infer R}`
  ? TrimLeft<R>
  : T;

实现 Trim，TrimRight

Trim

type Space = `${" " | "\t" | "\n"}`;
type Trim<T extends string> = T extends
  | `${Space}${infer R}`
  | `${infer R}${Space}`
  ? Trim<R>
  : T;

TrimRight

type Space = `${" " | "\t" | "\n"}`;
type TrimRight<T extends string> = T extends `${infer R}${Space}`
  ? TrimRight<R>
  : T;