Senior UI Software Engineer Interview Questions and Answers

Implement a React stopwatch with start, stop, resume, and pause functionalities.

• Use state to track the elapsed time

• Create functions for start, stop, resume, and pause actions

• Use setInterval for updating the timer every second

• Display the timer in the UI

Memory leaks in JavaScript happen when unused objects are not properly released from memory.

• Memory leaks can occur when variables are not properly dereferenced, preventing garbage collection.

• Closures can also lead to memory leaks if they hold references to large objects.

• Event listeners can cause memory leaks if not removed properly after use.

• Using setInterval without clearing it can lead to memory leaks.

• Circular references can also cause memory leaks in JavaScript.

Implement a curried sum function that allows chaining of arguments and returns the total when called with no arguments.

• Currying transforms a function with multiple arguments into a sequence of functions each taking a single argument.

• The sum function should return another function that takes a number and adds it to the accumulated sum.

• When called with no arguments, it should return the total sum of all previously provided arguments.

• Example: sum(1)(2)(3)() should return 6.

Error handling in React involves creating a component to display error messages and handling errors gracefully.

• Create an ErrorBoundary component to catch errors in child components.

• Use try-catch blocks in async functions to handle errors.

• Display error messages to the user using state or props.

• Use error boundaries to prevent the entire UI from crashing due to a single error.