Senior Javascript Developer Interview Questions

158 senior javascript developer interview questions shared by candidates

- variable hoisting - event loop - javascript variable scope - difference between let, const, var, function - typecasting in javascript - difference between primary data type & wrapper classes - call by value & call by reference - AWS services like EC2, S3, SQS, SNS, ECR, lambda, step functions - system design for big data download from database using AWS services
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Senior Full Stack Javascript Developer

Interviewed at Velotio

4
Aug 6, 2023

- variable hoisting - event loop - javascript variable scope - difference between let, const, var, function - typecasting in javascript - difference between primary data type & wrapper classes - call by value & call by reference - AWS services like EC2, S3, SQS, SNS, ECR, lambda, step functions - system design for big data download from database using AWS services

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
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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

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