Drop Char

In this medium-level challenge, you'll implement the DropChar<S, C> type, that drops a specified char from a string.

[object Object]

// Video Solution: https://youtube.com/watch?v=vxrp7FnY_zw

type cases = [
  // @ts-expect-error
  Expect<Equal<DropChar<'butter fly!', ''>, 'butterfly!'>>,
  Expect<Equal<DropChar<'butter fly!', ' '>, 'butterfly!'>>,
  Expect<Equal<DropChar<'butter fly!', '!'>, 'butter fly'>>,
  Expect<Equal<DropChar<'    butter fly!        ', ' '>, 'butterfly!'>>,
  Expect<Equal<DropChar<' b u t t e r f l y ! ', ' '>, 'butterfly!'>>,
  Expect<Equal<DropChar<' b u t t e r f l y ! ', 'b'>, '  u t t e r f l y ! '>>,
  Expect<Equal<DropChar<' b u t t e r f l y ! ', 't'>, ' b u   e r f l y ! '>>,
]

Detailed Explanation

type DropChar<S, C extends string> = S extends `${infer Left}${C}${infer Right}`
  ? DropChar<`${Left}${Right}`, C>
  : S

How it works:

• First we constrain the type C to be a string.
• Then we use a template literal and infer to capture the the left and right parts of the string, surrounding the character to drop.
• If the character to drop is found, we recursively pass the left and right parts of the string into DropChar<${Left}${Right}, C>.
• If the character to drop is not found, we return the original string.

This challenge helps you understand TypeScript's advanced type system and how to apply this concept in real-world scenarios.