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Adam LaCombe
Adam LaCombe

Posted on • Originally published at adamlacombe.com on

How to pick properties from an interface

#webdev #beginners #typescript

You can use the built-in type Pick. Pick<MyInterface, "prop1" | "prop2"> is a built-in type which allows you to pick specific properties from an interface.

A great use-case would be verifying user credentials. You might have a User interface such as the following:

interface User { id: number; firstName: string; lastName: string; email: string; password: string; }
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Instead of creating a new interface with the email and password properties from the User interface, lets Pick them!

// without Pick async function verifyLoginCredentials(credentials: { email: string, password: string }) { // ... ... } // with Pick async function verifyLoginCredentials(credentials: Pick<User, "email" | "password">) { const user = await getUserByEmail(credentials.email); if (!passwordMatches(credentials.password, user.password)) { throw new BadRequestError('incorrect password'); } return user; } verifyLoginCredentials({ email: "example@example.com", password: "123" });
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