What is promise chaining and error handling?

Promise chaining passes resolved values through then handlers and routes thrown errors or rejections to catch handlers. In an interview, support it with one tradeoff and one production example.

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Top 10 JavaScripte Questions in 2026

Q: What is the event loop in JavaScript?

The event loop runs queued asynchronous work when the call stack is empty, prioritizing microtasks such as Promise callbacks before macrotasks such as timers. In an interview, support it with one tradeoff and one production example.

Q: How do closures work in JavaScript?

A closure lets a function keep access to variables from its lexical scope even after the outer function has finished executing. In an interview, support it with one tradeoff and one production example.

Written by RivoHire Team

Published on Jun 18, 2026 · 13 min read

Top 10 JavaScripte Questions in 2026 uses verified RivoHire qbank answers. Start with the strongest short answer, then review tradeoffs, scenarios, mistakes, and interview wording.

JavascriptJavascriptTop 10 Javascripte Questions In 2026Javascript Interview Questions

Quick Summary

Topic	Questions	Source	Company Claims
Javascript	10	MongoDB qbank	Only shown when present in qbank

Scenario Questions

A dashboard freezes while processing a large response on the browser main thread. I would split CPU-heavy work, keep promise chains predictable, and verify improvement with interaction latency and long-task measurements.
A JavaScript change causes slower responses after traffic increases. I would isolate the hot path, apply the smallest reversible fix, and verify the result with latency, error rate, and rollback readiness.
A JavaScript change causes slower responses after traffic increases. I would isolate the hot path, apply the smallest reversible fix, and verify the result with latency, error rate, and rollback readiness.
A JavaScript change causes slower responses after traffic increases. I would isolate the hot path, apply the smallest reversible fix, and verify the result with latency, error rate, and rollback readiness.

Common Mistakes

Wrong approach: event-loop is good because it is faster. Why it fails: Speed without workload, correctness, and operational context is not an engineering answer. Better answer: I would compare the workload, failure mode, and maintenance cost before using event-loop, then verify the result with production metrics.
Wrong approach: closures is good because it is faster. Why it fails: Speed without workload, correctness, and operational context is not an engineering answer. Better answer: I would compare the workload, failure mode, and maintenance cost before using closures, then verify the result with production metrics.
Wrong approach: scope is good because it is faster. Why it fails: Speed without workload, correctness, and operational context is not an engineering answer. Better answer: I would compare the workload, failure mode, and maintenance cost before using scope, then verify the result with production metrics.
Wrong approach: promises is good because it is faster. Why it fails: Speed without workload, correctness, and operational context is not an engineering answer. Better answer: I would compare the workload, failure mode, and maintenance cost before using promises, then verify the result with production metrics.
Wrong approach: setTimeout with zero delay runs immediately. Why it fails: It waits for the current stack and microtasks to finish. Better answer: Zero delay means schedule as a macrotask as soon as the stack and microtasks are clear.

FAQ

Practice

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Compact Interview Questions

What is the event loop in JavaScript?

The event loop coordinates the call stack, task queues, microtasks, and asynchronous callbacks.

How do closures work in JavaScript?

A closure lets a function retain access to variables from its lexical scope after the outer function has returned.

What is the difference between var, let, and const?

var is function-scoped and hoisted, while let and const are block-scoped; const prevents reassignment.

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