Use ?. to safely access nested properties:
let user = { name: "Alice" }
console.log(user.address?.city) // undefined (no error)
console.log(user.address?.city ?? "Unknown") // "Unknown"
let user2 = { address: { city: "Seattle" } }
console.log(user2.address?.city) // "Seattle"
Without ?., accessing user.address.city would throw an error because address is undefined.