# Why does this map return undefined values?

**URL:** <https://forum.kirupa.com/t/why-does-this-map-return-undefined-values/679739>\
**Category:** web dev\
**Created:** [March 31, 2026, 5:00am UTC](https://forum.kirupa.com/t/why-does-this-map-return-undefined-values/679739 "2026-03-31T05:00:04Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ellen1979](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/ellen1979/32/31260_2.png) [@Ellen1979](https://forum.kirupa.com/u/Ellen1979)\
**Post date:** [March 31, 2026, 5:00am UTC](https://forum.kirupa.com/t/why-does-this-map-return-undefined-values/679739/1 "2026-03-31T05:00:04Z")

</div>

Consider this snippet.

```javascript
const nums = [1, 2, 3];
const out = nums.map((n) => { n * 2; });
console.log(out);

```

Why is the output not `[2, 4, 6]`, and what is the simplest fix.

Ellen

---

<div class="post-metadata">

**Author:** ![Quelly](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/quelly/32/31386_2.png) [@Quelly](https://forum.kirupa.com/u/Quelly)\
**Post date:** [March 31, 2026, 5:14am UTC](https://forum.kirupa.com/t/why-does-this-map-return-undefined-values/679739/2 "2026-03-31T05:14:05Z")

</div>

`map` uses the callback’s return value, and with `{}` your arrow function returns nothing, so you get `[undefined, undefined, undefined]`.

Quelly