Lesson

Optional chaining

A vacant lot has no house yet. Reading a key on undefined crashes. ?. means "if this part exists, keep going; if not, give undefined and stop."

const lot = { tag: "Ada" };
lot.house.flag     // crash — house is missing
lot.house?.flag    // undefined

Empty Colonia is full of missing houses. You will see ?. on almost every page that reads a plot.