Refer: Medium - Trim Left

Describe

Implement TrimLeft<T> which takes an exact string type and returns a new string with the whitespace beginning removed.

For example

code snippetCopytypescript
type trimed = TrimLeft<'  Hello World  '> // expected to be 'Hello World  '

Test Cases

code snippetCopytypescript
import { 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 '>>,
]

Solution

code snippetCopytypescript
type TrimLeft<S extends string> = S extends `${' ' | '\n' | '\t'}${infer P}` ? TrimLeft<P> : S