add some medium ts challenges

Author: diaz-rodrigo

Languages/Typescript/Generics/00002-medium-get-return-type.ts

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+/*
+  2 - Get Return Type
+  -------
+  by Anthony Fu (@antfu) #medium #infer #built-in
+
+  ### Question
+
+  Implement the built-in `ReturnType<T>` generic without using it.
+
+  For example
+
+  ```ts
+  const fn = (v: boolean) => {
+    if (v)
+      return 1
+    else
+      return 2
+  }
+
+  type a = MyReturnType<typeof fn> // should be "1 | 2"
+  ```
+
+  > View on GitHub: https://tsch.js.org/2
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type MyReturnType<T extends (...args: any[]) => any> = T extends (
+  ...args: any[]
+) => infer R
+  ? R
+  : never;
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+type cases = [
+  Expect<Equal<string, MyReturnType<() => string>>>,
+  Expect<Equal<123, MyReturnType<() => 123>>>,
+  Expect<Equal<ComplexObject, MyReturnType<() => ComplexObject>>>,
+  Expect<Equal<Promise<boolean>, MyReturnType<() => Promise<boolean>>>>,
+  Expect<Equal<() => "foo", MyReturnType<() => () => "foo">>>,
+  Expect<Equal<1 | 2, MyReturnType<typeof fn>>>,
+  Expect<Equal<1 | 2, MyReturnType<typeof fn1>>>
+];
+
+type ComplexObject = {
+  a: [12, "foo"];
+  bar: "hello";
+  prev(): number;
+};
+
+const fn = (v: boolean) => (v ? 1 : 2);
+const fn1 = (v: boolean, w: any) => (v ? 1 : 2);
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/2/answer
+  > View solutions: https://tsch.js.org/2/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/00003-medium-omit.ts

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+/*
+  3 - Omit
+  -------
+  by Anthony Fu (@antfu) #medium #union #built-in
+
+  ### Question
+
+  Implement the built-in `Omit<T, K>` generic without using it.
+
+  Constructs a type by picking all properties from `T` and then removing `K`
+
+  For example
+
+  ```ts
+  interface Todo {
+    title: string
+    description: string
+    completed: boolean
+  }
+
+  type TodoPreview = MyOmit<Todo, 'description' | 'title'>
+
+  const todo: TodoPreview = {
+    completed: false,
+  }
+  ```
+
+  > View on GitHub: https://tsch.js.org/3
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type MyOmit<T , K extends keyof T> = {
+  [P in keyof T as P extends K ? never : P] : T[P] 
+} 
+
+type TodoPreview = MyOmit<Todo, 'description' | 'title'>
+
+  const todo: TodoPreview = {
+    completed: false,
+  }
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from '@type-challenges/utils'
+
+type cases = [
+  Expect<Equal<Expected1, MyOmit<Todo, 'description'>>>,
+  Expect<Equal<Expected2, MyOmit<Todo, 'description' | 'completed'>>>,
+]
+
+// @ts-expect-error
+type error = MyOmit<Todo, 'description' | 'invalid'>
+
+interface Todo {
+  title: string
+  description: string
+  completed: boolean
+}
+
+interface Expected1 {
+  title: string
+  completed: boolean
+}
+
+interface Expected2 {
+  title: string
+}
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/3/answer
+  > View solutions: https://tsch.js.org/3/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/00268-easy-if.ts

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+/*
+  268 - If
+  -------
+  by Pavel Glushkov (@pashutk) #easy #utils
+
+  ### Question
+
+  Implement the util type `If<C, T, F>` which accepts condition `C`, a truthy value `T`, and a falsy value `F`. `C` is expected to be either `true` or `false` while `T` and `F` can be any type.
+
+  For example:
+
+  ```ts
+  type A = If<true, 'a', 'b'>  // expected to be 'a'
+  type B = If<false, 'a', 'b'> // expected to be 'b'
+  ```
+
+  > View on GitHub: https://tsch.js.org/268
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type If<C extends boolean, T, F> = C extends true ? T : F 
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from '@type-challenges/utils'
+
+type cases = [
+  Expect<Equal<If<true, 'a', 'b'>, 'a'>>,
+  Expect<Equal<If<false, 'a', 2>, 2>>,
+]
+
+// @ts-expect-error
+type error = If<null, 'a', 'b'>
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/268/answer
+  > View solutions: https://tsch.js.org/268/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/00533-easy-concat.ts

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+/*
+  533 - Concat
+  -------
+  by Andrey Krasovsky (@bre30kra69cs) #easy #array
+
+  ### Question
+
+  Implement the JavaScript `Array.concat` function in the type system. A type takes the two arguments. The output should be a new array that includes inputs in ltr order
+
+  For example:
+
+  ```ts
+  type Result = Concat<[1], [2]> // expected to be [1, 2]
+  ```
+
+  > View on GitHub: https://tsch.js.org/533
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type Tuple = readonly unknown[];
+
+type Concat<T extends Tuple, U extends Tuple> = [...T, ...U]
+type Result2 = Concat<[], []>; // expected to be [1, 2]
+type Result3 = Concat<[], [1]>; // expected to be [1]
+type Result = Concat<[1], [2]>; // expected to be [1, 2]
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+const tuple = [1] as const;
+
+type cases = [
+  Expect<Equal<Concat<[], []>, []>>,
+  Expect<Equal<Concat<[], [1]>, [1]>>,
+  Expect<Equal<Concat<[1], [2]>, [1, 2]>>,
+  Expect<Equal<Concat<typeof tuple, typeof tuple>, [1, 1]>>,
+  Expect<Equal<Concat<[1, 2], [3, 4]>, [1, 2, 3, 4]>>,
+  Expect<
+    Equal<
+      Concat<["1", 2, "3"], [false, boolean, "4"]>,
+      ["1", 2, "3", false, boolean, "4"]
+    >
+  >
+];
+
+// @ts-expect-error
+type error = Concat<null, undefined>;
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/533/answer
+  > View solutions: https://tsch.js.org/533/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/00898-easy-includes.ts

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+/*
+  898 - Includes
+  -------
+  by null (@kynefuk) #easy #array
+
+  ### Question
+
+  Implement the JavaScript `Array.includes` function in the type system. A type takes the two arguments. The output should be a boolean `true` or `false`.
+
+  For example:
+
+  ```ts
+  type isPillarMen = Includes<['Kars', 'Esidisi', 'Wamuu', 'Santana'], 'Dio'> // expected to be `false`
+  ```
+
+  > View on GitHub: https://tsch.js.org/898
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type Includes<T extends readonly any[], U> = {
+  [P in T[number]] : true 
+}[U] extends true ? true : false
+
+
+type isPillarMen = Includes<["Kars", "Esidisi", "Wamuu", "Santana"], "Dio">; // expected to be `false`
+type isPillarMen2 = Includes<["Kars", "Esidisi", "Wamuu", "Santana"], "Kars">; // expected to be `true`
+type isPillarMen3 = Includes<[{}], { a: "A" }>; // expected to be `false`
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+type cases = [
+  Expect<Equal<Includes<[{}], { a: "A" }>, false>>,
+  Expect<
+    Equal<Includes<["Kars", "Esidisi", "Wamuu", "Santana"], "Kars">, true>
+  >,
+  Expect<
+    Equal<Includes<["Kars", "Esidisi", "Wamuu", "Santana"], "Dio">, false>
+  >,
+
+  Expect<Equal<Includes<[1, 2, 3, 5, 6, 7], 7>, true>>,
+  Expect<Equal<Includes<[1, 2, 3, 5, 6, 7], 4>, false>>,
+  Expect<Equal<Includes<[1, 2, 3], 2>, true>>,
+  Expect<Equal<Includes<[1, 2, 3], 1>, true>>,
+  Expect<Equal<Includes<[boolean, 2, 3, 5, 6, 7], false>, false>>,
+  Expect<Equal<Includes<[true, 2, 3, 5, 6, 7], boolean>, false>>,
+  Expect<Equal<Includes<[false, 2, 3, 5, 6, 7], false>, true>>,
+  Expect<Equal<Includes<[{ a: "A" }], { readonly a: "A" }>, false>>,
+  Expect<Equal<Includes<[{ readonly a: "A" }], { a: "A" }>, false>>,
+  Expect<Equal<Includes<[1], 1 | 2>, false>>,
+  Expect<Equal<Includes<[1 | 2], 1>, false>>,
+  Expect<Equal<Includes<[null], undefined>, false>>,
+  Expect<Equal<Includes<[undefined], null>, false>>
+];
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/898/answer
+  > View solutions: https://tsch.js.org/898/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/03057-easy-push.ts

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+/*
+  3057 - Push
+  -------
+  by jiangshan (@jiangshanmeta) #easy #array
+
+  ### Question
+
+  Implement the generic version of ```Array.push```
+
+  For example:
+
+  ```typescript
+  type Result = Push<[1, 2], '3'> // [1, 2, '3']
+  ```
+
+  > View on GitHub: https://tsch.js.org/3057
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type Push<T extends any[], U> = U extends any[]
+  ? [...T, ...U]
+  : U extends boolean
+  ? [...T, boolean]
+  : [...T, U];
+
+type Result = Push<[1, 2], boolean>; // [1, 2, boolean]
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+type cases = [
+  Expect<Equal<Push<[], 1>, [1]>>,
+  Expect<Equal<Push<[1,2,3], [4,5 ,boolean]>, [1, 2, 3, 4, 5, boolean,]>>,
+  Expect<Equal<Push<[1, 2], "3">, [1, 2, "3"]>>,
+  Expect<Equal<Push<["1", 2, "3"], boolean>, ["1", 2, "3", boolean]>>
+];
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/3057/answer
+  > View solutions: https://tsch.js.org/3057/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/03060-easy-unshift.ts

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+/*
+  3060 - Unshift
+  -------
+  by jiangshan (@jiangshanmeta) #easy #array
+
+  ### Question
+
+  Implement the type version of ```Array.unshift```
+
+  For example:
+
+  ```typescript
+  type Result = Unshift<[1, 2], 0> // [0, 1, 2,]
+  ```
+
+  > View on GitHub: https://tsch.js.org/3060
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type Unshift<T extends any[], U> = [U, ...T]
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from '@type-challenges/utils'
+
+type cases = [
+  Expect<Equal<Unshift<[], 1>, [1]>>,
+  Expect<Equal<Unshift<[1, 2], 0>, [0, 1, 2]>>,
+  Expect<Equal<Unshift<['1', 2, '3'], boolean>, [boolean, '1', 2, '3']>>,
+]
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/3060/answer
+  > View solutions: https://tsch.js.org/3060/solutions
+  > More Challenges: https://tsch.js.org
+*/