TypeScript Pick: Select Properties from a Type (Examples)

Pick<T, K> is a built-in utility type that creates an object type with only the properties of T named in K. Use it when a function or component needs a few fields of a bigger type:

interface User {
  id: number;
  name: string;
  email: string;
  passwordHash: string;
  lastLogin: string;
}

type UserPreview = Pick<User, "id" | "name">;
// { id: number; name: string }

function renderPreview(user: UserPreview): string {
  return `#${user.id} ${user.name}`;
}

const ada: User = {
  id: 1, name: "Ada", email: "ada@example.com",
  passwordHash: "x9f...", lastLogin: "2024-03-15",
};

console.log(renderPreview(ada));                  // #1 Ada
console.log(renderPreview({ id: 2, name: "Linus" })); // #2 Linus

renderPreview accepts a full User and also a plain { id, name } object, because it asks for only what it uses. That makes it easier to call and to test. Pick is type-only: the full ada object still has all five properties at runtime.

Syntax and Key Checking

Pick<Type, Keys>

Keys is a single key or a union of keys, and each one must exist on Type. The definition in TypeScript's standard library makes that a constraint:

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

Because of K extends keyof T, a misspelled or missing key is a compile error, and your editor can autocomplete the key names:

interface Product {
  sku: string;
  title: string;
  price: number;
  stock: number;
}

type PriceTag = Pick<Product, "title" | "price">;

const tag: PriceTag = { title: "Lamp", price: 39 };
console.log(`${tag.title}: $${tag.price}`); // Lamp: $39

// @ts-expect-error: Type '"cost"' does not satisfy the constraint 'keyof Product'
type Broken = Pick<Product, "cost">;

The error is error TS2344: Type '"cost"' does not satisfy the constraint 'keyof Product'. This is a difference from Omit, whose keys are not checked.

Pick Keeps readonly and Optional

Pick maps over keys of T, so each picked property keeps its modifiers:

interface Account {
  readonly id: number;
  email?: string;
  plan: "free" | "pro";
}

type AccountRef = Pick<Account, "id" | "email">;
// { readonly id: number; email?: string }

const ref: AccountRef = { id: 7 }; // email is still optional
// @ts-expect-error: Cannot assign to 'id' because it is a read-only property
ref.id = 8;

console.log(ref); // { id: 8 }

The last line shows { id: 8 } because readonly is a compile-time check only: the assignment was reported, suppressed with @ts-expect-error, and still ran. To change the modifiers as you pick, wrap the result: Partial<Pick<Account, "plan">> or Required<Pick<Account, "email">>.

Pick vs Omit

Pick names what to keep; Omit names what to drop. Both give the same result today, but they behave differently when the source type grows:

interface Order {
  id: number;
  total: number;
  cardLast4: string;
  // added later: internalNotes: string;
}

type Receipt = Pick<Order, "id" | "total">;   // stays { id; total }
type AdminView = Omit<Order, "cardLast4">;    // will include internalNotes too

const receipt: Receipt = { id: 1, total: 49.9 };
const admin: AdminView = { id: 1, total: 49.9 };
console.log(receipt, admin); // { id: 1, total: 49.9 } { id: 1, total: 49.9 }

For data that leaves your server, Pick is the safer default: nothing appears in the type unless someone added it on purpose.

Picking from Nested Types

Pick only sees top-level keys: a dotted path like Pick<Customer, "address.city"> is an error (TS2344), not a nested pick. Use an indexed access type to reach the nested type, then pick from it:

interface Customer {
  id: number;
  name: string;
  address: {
    street: string;
    city: string;
    country: string;
  };
}

type City = Pick<Customer["address"], "city">; // { city: string }

// Keep the shape, trim the nested object
type ShippingLabel = Pick<Customer, "name"> & {
  address: Pick<Customer["address"], "city" | "country">;
};

const label: ShippingLabel = {
  name: "Ada",
  address: { city: "London", country: "UK" },
};

const city: City = { city: label.address.city };
console.log(label, city.city);
// { name: 'Ada', address: { city: 'London', country: 'UK' } } London

Customer["address"] is the type of the address property. The same syntax reaches array elements: for an orders: Order[] property, Customer["orders"][number] is Order.

A Typed pick() Function

Pick does nothing at runtime. A small generic function copies the chosen properties into a new object and returns exactly Pick<T, K>:

function pick<T extends object, K extends keyof T>(obj: T, ...keys: K[]): Pick<T, K> {
  const result = {} as Pick<T, K>;
  for (const key of keys) {
    result[key] = obj[key];
  }
  return result;
}

const book = { id: 3, title: "Dune", author: "Herbert", pages: 412 };

const summary = pick(book, "title", "author"); // { title: string; author: string }
console.log(summary);          // { title: 'Dune', author: 'Herbert' }
console.log(Object.keys(summary)); // [ 'title', 'author' ]
// pick(book, "isbn") would be error TS2345: Argument of type '"isbn"' is not assignable
// to parameter of type '"author" | "id" | "pages" | "title"'.

K extends keyof T lets TypeScript infer K from the string arguments, so the return type has exactly the picked keys. The {} as Pick<T, K> assertion is needed because an empty object does not have those properties yet; the loop fills them in.

Picking Properties by Value Type

Pick selects by key name. To select by the property's type, for example "all the string fields", write a mapped type with a key filter:

type PickByValue<T, V> = {
  [P in keyof T as T[P] extends V ? P : never]: T[P];
};

interface Article {
  id: number;
  title: string;
  slug: string;
  views: number;
  published: boolean;
}

type TextFields = PickByValue<Article, string>;   // { title: string; slug: string }
type NumberFields = PickByValue<Article, number>; // { id: number; views: number }

const text: TextFields = { title: "Hello", slug: "hello" };
const nums: NumberFields = { id: 1, views: 120 };
console.log(text, nums); // { title: 'Hello', slug: 'hello' } { id: 1, views: 120 }

The as clause maps each key to itself when its type matches and to never otherwise, and never keys are dropped. One subtlety: an optional property's type includes undefined, so an optional subtitle?: string would not count as string here; test against string | undefined to include it.