TypeScript optional property (3)

retool-typescript-control-flow-analysis-18.ts

interface Person {
  name: string
  address?: {
    city: string
    zipcode: string
  }
}

const person: Person = { name: "John", address: undefined }

function printUserInfo(p: Person) {
  for (const prop in p) {
    console.log(prop, p[prop])
  }
}

printUserInfo(person)
// Prints:
//  > "name", "John"
//  > "address", undefined