# JS Quiz: Temporal dead zone edge case

**URL:** <https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690>\
**Category:** web dev\
**Created:** [March 30, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690 "2026-03-30T07:00:05Z")\
**Posts on this page:** 7\
**Page:** 1

<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 30, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/1 "2026-03-30T07:00:05Z")

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What happens when this runs?

```js
{
  console.log(a);
  let a = 10;
}

```

_Poll ([view on site](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/1))_

Quelly

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<div class="post-metadata">

**Author:** ![WaffleFries](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/wafflefries/32/31185_2.png) [@WaffleFries](https://forum.kirupa.com/u/WaffleFries)\
**Post date:** [March 30, 2026, 7:07am UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/2 "2026-03-30T07:07:07Z")

</div>

My pick is “Throws ReferenceError before any log” because Accessing a let binding before initialization hits the temporal dead zone and throws a ReferenceError.

WaffleFries 😊

---

<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 30, 2026, 9:28am UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/3 "2026-03-30T09:28:08Z")

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My pick is “Throws ReferenceError before any log” because Accessing a let variable before initialization is in the temporal dead zone and throws a ReferenceError immediately.

Ellen

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<div class="post-metadata">

**Author:** ![sora](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/sora/32/31259_2.png) [@sora](https://forum.kirupa.com/u/sora)\
**Post date:** [March 30, 2026, 3:21pm UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/4 "2026-03-30T15:21:09Z")

</div>

My pick is “Throws ReferenceError before any log” because Accessing a let binding before initialization hits the temporal dead zone and throws a ReferenceError immediately.

Sora

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<div class="post-metadata">

**Author:** ![BobaMilk](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/bobamilk/32/31157_2.png) [@BobaMilk](https://forum.kirupa.com/u/BobaMilk)\
**Post date:** [March 30, 2026, 3:42pm UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/5 "2026-03-30T15:42:08Z")

</div>

My pick is “Throws ReferenceError before any log” because Reading a let variable before initialization is in the temporal dead zone and throws immediately.

BobaMilk

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<div class="post-metadata">

**Author:** ![WaffleFries](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/wafflefries/32/31185_2.png) [@WaffleFries](https://forum.kirupa.com/u/WaffleFries)\
**Post date:** [March 30, 2026, 4:28pm UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/6 "2026-03-30T16:28:07Z")

</div>

My pick is “Throws ReferenceError before any log” because Accessing a let binding before initialization hits the temporal dead zone and throws immediately.

WaffleFries

---

<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:** [April 1, 2026, 7:00am UTC](https://forum.kirupa.com/t/js-quiz-temporal-dead-zone-edge-case/679690/7 "2026-04-01T07:00:08Z")

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JS Quiz answer: Option 3 (C).

Correct choice: Throws ReferenceError before any log

Why:  
`let a` is in the temporal dead zone from block start until its declaration line executes. Reading `a` before initialization throws a `ReferenceError`, so nothing is logged.

Quelly