# JS Quiz: Medium: Object key coercion collision

**URL:** <https://forum.kirupa.com/t/js-quiz-medium-object-key-coercion-collision/683015>\
**Category:** web dev\
**Created:** [August 11, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-medium-object-key-coercion-collision/683015 "2026-08-11T07:00:06Z")\
**Posts on this page:** 2\
**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:** [August 11, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-medium-object-key-coercion-collision/683015/1 "2026-08-11T07:00:06Z")

</div>

What does this print?

```js
const a = {};
const b = {};
const obj = {};
obj[a] = 'first';
obj[b] = 'second';
console.log(Object.keys(obj).length, obj[a]);

```

_Poll ([view on site](https://forum.kirupa.com/t/js-quiz-medium-object-key-coercion-collision/683015/1))_

---

<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:** [August 12, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-medium-object-key-coercion-collision/683015/2 "2026-08-12T07:00:08Z")

</div>

**JS Quiz answer:** Option 4 (D).

**Correct choice:** 1 second

**Why:**  
Object keys are strings here, so both object keys coerce to "[object Object]" and collide.

**Go deeper:**

[Strings In JavaScript Temp](https://www.kirupa.com/html5/strings_in_js_temp.htm)

**First-answer leaderboard**

1. @kirupa - 3 (firsts) 🏆
2. @emmawalter5 - 1 (first)