add 2 ts medium challenges

Author: diaz-rodrigo

Languages/Typescript/Generics/02070-medium-drop-char.ts

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+/*
+  2070 - Drop Char
+  -------
+  by CaptainOfPhB (@CaptainOfPhB) #medium #template-literal #infer
+
+  ### Question
+
+  Drop a specified char from a string.
+
+  For example:
+
+  ```ts
+  type Butterfly = DropChar<' b u t t e r f l y ! ', ' '> // 'butterfly!'
+  ```
+
+  > View on GitHub: https://tsch.js.org/2070
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type DropChar<S, C> = S extends `${infer H}${infer T}`
+  ? `${H extends C ? "" : H}${DropChar<T, C>}`
+  : S;
+
+type Butterfly = DropChar<" b u t t e r f l y ! ", " ">; // 'butterfly!'
+//  ^?
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+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 ! ">>
+];
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/2070/answer
+  > View solutions: https://tsch.js.org/2070/solutions
+  > More Challenges: https://tsch.js.org
+*/

Languages/Typescript/Generics/02595-medium-pickbytype.ts

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+/*
+  2595 - PickByType
+  -------
+  by jiangshan (@jiangshanmeta) #medium #object
+
+  ### Question
+
+  From `T`, pick a set of properties whose type are assignable to `U`.
+
+  For Example
+
+  ```typescript
+  type OnlyBoolean = PickByType<{
+    name: string
+    count: number
+    isReadonly: boolean
+    isEnable: boolean
+  }, boolean> // { isReadonly: boolean; isEnable: boolean; }
+  ```
+
+  > View on GitHub: https://tsch.js.org/2595
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type PickByType<T, U> = {
+  [K in keyof T as T[K] extends U ? K : never]: T[K];
+};
+
+type OnlyBoolean = PickByType<
+  {
+    name: string;
+    count: number;
+    isReadonly: boolean;
+    isEnable: boolean;
+  },
+  boolean
+>;
+
+const onlyBoolean: OnlyBoolean = { isEnable: false, isReadonly: true };
+//         ^?
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+interface Model {
+  name: string;
+  count: number;
+  isReadonly: boolean;
+  isEnable: boolean;
+}
+
+type cases = [
+  Expect<
+    Equal<
+      PickByType<Model, boolean>,
+      { isReadonly: boolean; isEnable: boolean }
+    >
+  >,
+  Expect<Equal<PickByType<Model, string>, { name: string }>>,
+  Expect<Equal<PickByType<Model, number>, { count: number }>>
+];
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/2595/answer
+  > View solutions: https://tsch.js.org/2595/solutions
+  > More Challenges: https://tsch.js.org
+*/