# JS Quiz: Easy: Map key identity with NaN

**URL:** <https://forum.kirupa.com/t/js-quiz-easy-map-key-identity-with-nan/683791>\
**Category:** web dev\
**Created:** [October 20, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-easy-map-key-identity-with-nan/683791 "2026-10-20T07:00:05Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yoshiii](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/yoshiii/32/31156_2.png) [@Yoshiii](https://forum.kirupa.com/u/Yoshiii)\
**Post date:** [October 20, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-easy-map-key-identity-with-nan/683791/1 "2026-10-20T07:00:06Z")

</div>

What is printed?

```js
const m = new Map();
m.set(NaN, 'first');
m.set(NaN, 'second');
console.log(m.size, m.get(NaN));

```

_Poll ([view on site](https://forum.kirupa.com/t/js-quiz-easy-map-key-identity-with-nan/683791/1))_