Type Challenge

Easy type challenges

Updated date: 2024-11-21

Type Challenge

• type-challenges

Solutons

• Hello World
  • answer

    type HelloWorld = string;
    

• Pick
  • answer

    type MyPick<T, K extends keyof T> = {
      [P in K]: T[P];
    };
    

  • tips
    • "|" represents union type
• Readonly
  • answer

    type MyReadonly<T> = {
      readonly [P in keyof T]: T[P];
    };
    

  • tips
    • "readonly" represents Readonly modifier
• Tuple to Object
  • answer

    type TupleToObject<T extends readonly PropertyKey[]> = {
      [key in T[number]]: key;
    };
    

  • tips
    • See Mapped Types
• First of Array
  • answer

    type First<T extends any[]> = T extends [] ? never : T[0];
    

  • tips
    • "never" represents never type
    • T extends [] is a specific check to determine if T is an empty array. It evaluates to true only if T is an empty array, allowing the type to distinguish between empty and non-empty arrays.
• Length of Tuple
  • answer

  type Length<T> = T extends readonly any[] ? T["length"] : Length<T>;
  

  • tips:
    • See Indexed Access Types
• Exclude
  • answer

    type MyExclude<T, U> = T extends U ? never : T;
    

• Awaited
  • answer

    type MyAwaited<T> = T extends Promise<infer K> ? MyAwaited<K> : T;
    

  • tips:
    • See Conditional Types
• If
  • answer

    type If<C extends boolean, T, F> = C extends true ? T : F;
    

• Concat
  • answer

    type Concat<T extends any[], U extends any[]> = [...T, ...U];
    

• Includes
  • answer

    type Includes<T extends readonly any[], U> = U extends T[number]
      ? true
      : false;
    

• Push
  • answer

    type Push<T extends any[], U> = [...T, U];
    

• Unshift
  • answer

    type Unshift<T extends any[], U> = [U, ...T];
    

• Parameters
  • answer

    type MyParameters<T extends (...args: any) => any> = T extends (
      ...args: infer P
    ) => any
      ? P
      : never;