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1,680 javascript interview questions shared by candidates

Event loop SOLID principles Currying - sum(1)(2)() - implementation Const Person = { Name Age setName() => arrow setAge: function() } console(Person.name) console(Person.age) Websocket, Polling requestAnimationFrame() RBAC, theme - context or store Union, intersection Git rebase, merge Partial, omit Testing library - jest, rtl Directives, composition Using ref - change button color useHistory - maintain prev and next array.map(a => a < 3) React fiber Prioritisation in react - how does it happen ssr, nextjs Liskov, IoC Code review Performance optimization - initial load 10s Garbage collection Memory optimization Critical rendering path when you use custom hook how would you maintain reference when its used across multiple components, something to do with useEffect Proto and prototypal inheritance Lifecycle hooks React versions Owasp top 10 Cors Xss How react handles xss V8 engine - implementation
avatar

Senior Javascript Developer

Interviewed at EPAM Systems

4★
Feb 18, 2026

Event loop SOLID principles Currying - sum(1)(2)() - implementation Const Person = { Name Age setName() => arrow setAge: function() } console(Person.name) console(Person.age) Websocket, Polling requestAnimationFrame() RBAC, theme - context or store Union, intersection Git rebase, merge Partial, omit Testing library - jest, rtl Directives, composition Using ref - change button color useHistory - maintain prev and next array.map(a => a < 3) React fiber Prioritisation in react - how does it happen ssr, nextjs Liskov, IoC Code review Performance optimization - initial load 10s Garbage collection Memory optimization Critical rendering path when you use custom hook how would you maintain reference when its used across multiple components, something to do with useEffect Proto and prototypal inheritance Lifecycle hooks React versions Owasp top 10 Cors Xss How react handles xss V8 engine - implementation

You have 10 boxes of balls (each ball weighing exactly 10 gm) with one box with defective balls (each one of the defective balls weigh 9 gm). You are given an electronic weighing machine and only one chance at it. How will find out which box has the defective balls?
avatar

Javascript Developer

Interviewed at Dassault Systèmes

3.9★
Aug 5, 2024

You have 10 boxes of balls (each ball weighing exactly 10 gm) with one box with defective balls (each one of the defective balls weigh 9 gm). You are given an electronic weighing machine and only one chance at it. How will find out which box has the defective balls?

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