#116Medium

Replace

Implement `Replace<S, From, To>` which replaces the string `From` with `To` in the given string `S`. Master TypeScript template literal types in this medium-level challenge on TypeScriptPro.

In this medium-level challenge, you'll implement Replace<S, From, To> which replaces the string From with To in the given string S - but only once.

Challenge Instructions: Replace

Medium

Implement Replace<S, From, To> which replace the string From with To once in the given string S

For example

[object Object]

Change the following code to make the test cases pass (no type check errors).

ChallengeSolution
// Video Solution: https://youtube.com/watch?v=yMFVdfvDI28

/* _____________ Your Code Here _____________ */

type Replace<S extends string, From extends string, To extends string> = any

/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '../helpers'

type cases = [
  Expect<Equal<Replace<'foobar', 'bar', 'foo'>, 'foofoo'>>,
  Expect<Equal<Replace<'foobarbar', 'bar', 'foo'>, 'foofoobar'>>,
  Expect<Equal<Replace<'foobarbar', '', 'foo'>, 'foobarbar'>>,
  Expect<Equal<Replace<'foobarbar', 'bar', ''>, 'foobar'>>,
  Expect<Equal<Replace<'foobarbar', 'bra', 'foo'>, 'fo

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Video Walkthrough

Detailed Explanation

type Replace<
  S extends string,
  From extends string,
  To extends string,
> = From extends ''
  ? S
  : S extends `${infer Before}${From}${infer After}`
    ? `${Before}${To}${After}`
    : S

How it works:

This challenge helps you understand TypeScript's template literal types and how to apply this concept in real-world scenarios.

This challenge is originally from here.

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