Lesson 7 — Interfaces: adding fields

Optional fields

Some fields are not always there — not every user gives an email. Put ? after the name (email?: string) to make a field optional: objects may leave it out, and TypeScript reminds you that reading it can give undefined.

interface Pet { name: string; nickname?: string }
const p: Pet = { name: "Rex" };           // ok without nickname
console.log(p.nickname ?? "no nickname");

Why it matters: it describes real forms and API data where some values are missing, and forces you to handle that case.