What is Pick?
The Pick utility type in TypeScript allows you to create a new type by selecting specific properties from an existing type. It is useful when you want to extract only certain properties from an object type and create a new type containing just those selected properties.
type Pick<T, K extends keyof T> = { [P in K]: T[P] };
How does Pick work?
Imagine you are building a React application, and you want to create a user card component that displays basic information, such as username and email, for users fetched from the https://jsonplaceholder.typicode.com/users API. Each user card should be clickable, leading to a more detailed page displaying additional information, such as the user's name and address.
We can declare User type like below.
interface User {
id: number;
name: string;
email: string;
username: string;
address: {
street: string;
suite: string;
city: string;
zipcode: string;
};
}
To create the user card component, we only require three pieces of information: the id (used as a key prop), username, and email. We'll define a UserCard type to represent this structure.
type UserCard = Pick<User, "id" | "username" | "email">;
This type will help us ensure the any data used for rendering the user card component contains these specific properties and display relevant information.
Recap
Hovering the cursor to UserCard after copying and pasting the code below to the editor, you will see the UserCard will display the 3 properties, id, username, and email.
interface User {
id: number;
name: string;
email: string;
username: string;
address: {
street: string;
suite: string;
city: string;
zipcode: string;
};
}
type UserCard = Pick<User, "id" | "username" | "email">;
In general, the Pick utility type serves as a valuable tool, enabling you to select specific properties tailored to your component's requirements, without the need to repeatedly rewrite those properties. It streamlines the process of cherry-picking essential properties, ensuring code efficiency and avoiding redundant declarations.
Resources
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Originally published at victoriacheng15.vercel.app