Frontend Virtual Onsite - Meta

All questions are from bigfrontenddev. It should be fine for frontend developers to practice these coding questions. Be careful not to memorize the answers, as there will be many follow-up questions. You need to thoroughly understand the questions and the underlying logic, understand why it should be written this way, and the pros and cons of different implementation methods.
1: debounce, throttle, memo
2: excludeItems, virtual dom II
3: design typehead
4: BQ