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1573 questions

What is the event loop in Node.js and how does it work?Node.js#runtimeJunior
Compare callbacks, Promises and async/await.Node.js#asyncJunior
What are streams in Node.js and when should you use them?Node.js#streamsMiddle
How do you scale a Node.js app across multiple CPUs?Node.js#scalingSenior
How do you detect and fix memory leaks in Node.js?Node.js#debuggingSenior
What is Node.js and what is it good for?Node.js#runtimeJunior
What is the difference between CommonJS and ES Modules in Node?Node.js#modulesJunior
What is npm and what do package.json and the lockfile do?Node.js#toolingJunior
What is the process object and what can it do?Node.js#runtimeJunior
How do you work with the file system in Node?Node.js#coreJunior
How do you create a basic HTTP server in Node?Node.js#coreJunior
What are Buffers in Node.js?Node.js#coreJunior
Why use the path module instead of string concatenation?Node.js#coreJunior
What is the EventEmitter and how is it used?Node.js#eventsMiddle
How does Express middleware work?Node.js#frameworkMiddle
How do you handle errors in async Node code?Node.js#error-handlingMiddle
How do you run external processes with child_process?Node.js#processMiddle
When and how do you use worker threads?Node.js#performanceMiddle
What utilities help work with async code (promisify, AbortController)?Node.js#asyncMiddle
How do you manage configuration and secrets in Node?Node.js#frameworkMiddle
What are npm scripts and lifecycle hooks?Node.js#toolingMiddle
How do you hash passwords and use the crypto module?Node.js#securityMiddle
What is CORS and how do you handle it in Node?Node.js#securityMiddle
What caching strategies improve a Node API's performance?Node.js#performanceMiddle
How do you profile and optimize Node.js performance?Node.js#performanceSenior
What are key security best practices for a Node.js app?Node.js#securitySenior
How do you implement graceful shutdown?Node.js#reliabilitySenior
What should you consider when building microservices in Node?Node.js#architectureSenior
How do you approach logging and monitoring in production Node?Node.js#reliabilitySenior
What is backpressure in streams and how do you handle it?Node.js#streamsSenior
What is the Virtual DOM and why does React use it?React#renderingJunior
What are the Rules of Hooks? Why can't you call a hook conditionally?React#hooksMiddle
When should you use useMemo and useCallback, and what problem do they solve?React#hooksSenior
What is JSX and how does it become JavaScript?React#jsxJunior
What is the difference between props and state?React#stateJunior
How does the useState hook work?React#hooksJunior
What is useEffect and when does it run?React#hooksJunior
Why do list items need a key, and why not use the index?React#renderingJunior
What is the difference between controlled and uncontrolled inputs?React#formsJunior
What are the ways to render content conditionally in React?React#renderingJunior
How does event handling work in React (synthetic events)?React#eventsJunior
What are React Fragments and why use them?React#renderingJunior
What are common pitfalls with the useEffect dependency array and cleanup?React#hooksMiddle
How does useContext and the Context API work?React#stateMiddle
When would you use useReducer instead of useState?React#hooksMiddle
What are the main use cases for useRef?React#hooksMiddle
What are custom hooks and how do you write one?React#hooksMiddle
What does "lifting state up" mean, and how does it relate to prop drilling?React#stateMiddle
What does React.memo do and when is it worth using?React#performanceMiddle
What are forwardRef and useImperativeHandle for?React#hooksMiddle