iTalent Digital interview question

Is JavaScript synchronous or asynchronous? What is the difference between var, let, and const? What is a closure in JavaScript? What is the Virtual DOM in React? Difference between controlled and uncontrolled components? Why doesn’t React re-render when state is mutated directly? Explain the event loop with microtasks and macrotasks. How does useEffect cleanup work? Difference between useMemo and useCallback? How does React batch state updates? How do you optimize performance in a React application? How do you handle large lists in React? What problems do React keys solve? How does React Fiber improve rendering performance? How would you design a reusable modal component in React?