Stackoverflow question, sample interfaces in Typescript

// Note: please restart the page if syntax highlighting works bad.
interface MyObject {
  id: number;
  name: string | null;
  age?: number | null;
  address?: string | null;
}

const myObj: MyObject = { id: 1, name: null, age: 30 };
function assignDefaults(a:MyObject, d:object)
{
  var r = a as MyObject;
  for (const k in d) {
      a[k] = a[k] ?? d[k];
  }
  return r;
}
// assignDefaults is my function
const newMyObj = assignDefaults(myObj, {
  name: 'Default Name',
  address: 'New York',
});

console.log(newMyObj) // desired output：{ id: 1, name: 'Default Name', age: 30, address: 'New York' }