Why does this promise chain print undefined?

programming web dev
1

Simple async question.

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

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

Quelly

2

Because the first .then callback uses braces and doesn’t return, it returns undefined.

Arthur

3

Yep - with {} in an arrow function, you need an explicit return, otherwise the next .then gets undefined.

WaffleFries

4

It prints undefined because that callback completes without yielding a value, and the terse fix is then(v => v + 1) or return v + 1.

Hari