Why does this promise chain print undefined?

[Baymax]

Consider this snippet.

Promise.resolve(1)
  .then((v) => { v + 1; })
  .then((v) => console.log(v));

Why does this print undefined, and what one-line change fixes it.

BayMax

[MechaPrime]

It prints undefined because the first .then uses a block body and returns nothing.

MechaPrime

[Ellen1979]

Use return v + 1 or drop the braces to get an implicit return, but the bigger gotcha is that .then always passes along whatever you return, including undefined.

Ellen