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JavaScript / V8 Engine Interview Questions 2026

Published July 22, 2026 · Updated July 22, 2026

6 JavaScript / V8 Engine interview questions from Amazon, Meta, Atlassian, Capgemini and more. Real questions from Technical, System Design, and HR rounds.

6 questions
Companies: Amazon, Meta, Atlassian, Capgemini

All JavaScript / V8 Engine Questions

Amazon Hard Screening round 4-7 years

What is tail call optimization and why doesn't JavaScript guarantee it despite ES6 spec?

↑ 80 upvotes · 8 engineers asked this · SDE2
Amazon Hard Screening round 4-7 years

Explain how garbage collection works in V8 (Node.js/Chrome). What causes GC pauses?

↑ 72 upvotes · 50 engineers asked this · SDE2
Meta Medium Technical round 1-4 yearsJavaScript

Explain the output order of this code and why: console.log(1); setTimeout(()=>console.log(2),0); Promise.resolve().then(()=>console.log(3)); console.log(4);

↑ 41 upvotes · 38 engineers asked this · Senior SDE
Capgemini Medium Technical round 1-4 yearsJavaScript

Write a function that creates 3 buttons where clicking button N alerts N, using a for loop and var. Explain why the naive version is broken and how to fix it.

↑ 25 upvotes · 18 engineers asked this · Developer
Atlassian Medium Technical round 2-5 yearsJavaScriptReact

A drag-and-drop board with 500+ cards becomes laggy while dragging. What specific JavaScript/DOM techniques would you use to keep the drag interaction smooth?

↑ 22 upvotes · 9 engineers asked this · Senior SDE
Amazon Hard Screening round 2-5 years

How does the event loop work in JavaScript? What is the difference between microtasks and macrotasks?

↑ 9 upvotes · 17 engineers asked this · SDE2

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Same topic at specific companies

Amazon JavaScript / V8 Engine Meta JavaScript / V8 Engine Atlassian JavaScript / V8 Engine Capgemini JavaScript / V8 Engine

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Frequently asked questions

What is tail call optimization and why doesn't JavaScript guarantee it despite ES6 spec?
What is tail call optimization and why doesn't JavaScript guarantee it despite ES6 spec?
Explain how garbage collection works in V8 (Node.js/Chrome). What causes GC pauses?
Explain how garbage collection works in V8 (Node.js/Chrome). What causes GC pauses?
Explain the output order of this code and why: console.log(1); setTimeout(()=>console.log(2),0); Promise.resolve().then(()=>console.log(3)); console.log(4);
Explain the output order of this code and why: console.log(1); setTimeout(()=>console.log(2),0); Promise.resolve().then(()=>console.log(3)); console.log(4);
Write a function that creates 3 buttons where clicking button N alerts N, using a for loop and var. Explain why the naive version is broken and how to fix it.
Write a function that creates 3 buttons where clicking button N alerts N, using a for loop and var. Explain why the naive version is broken and how to fix it.
A drag-and-drop board with 500+ cards becomes laggy while dragging. What specific JavaScript/DOM techniques would you use to keep the drag interaction smooth?
A drag-and-drop board with 500+ cards becomes laggy while dragging. What specific JavaScript/DOM techniques would you use to keep the drag interaction smooth?