How to specify optional properties in TypeScript?

TypeScript - Interview Questions

An object type can have zero or more optional properties by adding a ‘?’ after the property name.

let pt: { x: number; y: number; z?: number } = {
  x: 10,
  y: 20
};
console.log(pt);

In the example above, because the property ‘z’ is marked as optional, the compiler won’t complain if we don’t provide it during the initialization.