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Learning TypeScript 2.x - Second Edition
book

Learning TypeScript 2.x - Second Edition

by Remo H. Jansen
April 2018
Beginner content levelBeginner
536 pages
13h 21m
English
Packt Publishing
Content preview from Learning TypeScript 2.x - Second Edition

The keyof operator

The keyof operator can be used to generate a union type of the properties of an object as string literal types:

interface User {    name: string;    age: number;}type userKeys = keyof User; // "name" | "age"

The keyof operator can be used in combination with other operators, such as the typeof operator, for example:

let person = { name: "Remo", age: "28" };interface User {    name: string;    age: number;}type userKeys = keyof typeof person; // "name" | "age"

We will find out more about the keyof operator later in this chapter when we learn about lookup types.

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Publisher Resources

ISBN: 9781788391474Supplemental Content