Act as a senior JavaScript developer with 10+ years of experience. Explain the concept of closures in JavaScript in a way that is accessible to [BEGINNERS/INTERMEDIATE/ADVANCED] learners. Provide [THREE/FIVE/TEN] practical examples demonstrating how closures work, including use cases like [DATA ENCAPSULATION/EVENT HANDLERS/MEMOIZATION]. Break down each example step-by-step, highlighting how the lexical scope and function references create closures. Also, address common pitfalls such as [MEMORY LEAKS/UNINTENDED SCOPE RETENTION] and how to avoid them. End with a coding challenge where the learner must implement a closure to solve [A SPECIFIC PROBLEM, e.g., 'a counter with private state']. Use clear, concise language and avoid unnecessary jargon.