What does this promise chain log when one then callback forgets to return?

Promise.resolve(2)
  .then((x) => x * 10)
  .then((x) => {
    console.log(x);
    x + 1;
  })
  .then((x) => console.log(x))
  .then(() => Promise.resolve("done"))
  .then((x) => console.log(x));