Pick

introduction#

Implement the built-in Pick<T, K> generic without using it.

Constructs a type by picking the set of properties K from T

For example

ts
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
type MyPick<T, K> = any;
type TodoPreview = MyPick<Todo, 'title' | 'completed'>;
const todo: TodoPreview = {
  title: 'Clean room',
  completed: false,
};

ts
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
type MyPick<T, K> = any;
type TodoPreview = MyPick<Todo, 'title' | 'completed'>;
const todo: TodoPreview = {
  title: 'Clean room',
  completed: false,
};

View on GitHub

start point#

ts
/* _____________ Your Code Here _____________ */
type MyPick<T, K> = any;
 
/* _____________ Test Cases _____________ */
type cases = [
  Expect<Equal<Expected1, MyPick<Todo, 'title'>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<Expected2, MyPick<Todo, 'title' | 'completed'>>>
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.];
 
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
 
interface Expected1 {
  title: string;
}
 
interface Expected2 {
  title: string;
  completed: boolean;
}Try

ts
/* _____________ Your Code Here _____________ */
type MyPick<T, K> = any;
 
/* _____________ Test Cases _____________ */
type cases = [
  Expect<Equal<Expected1, MyPick<Todo, 'title'>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<Expected2, MyPick<Todo, 'title' | 'completed'>>>
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.];
 
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
 
interface Expected1 {
  title: string;
}
 
interface Expected2 {
  title: string;
  completed: boolean;
}Try

Take the Challenge

my solution#

Spoiler warning // Click to reveal answer

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

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

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