Imagine you're building a shopping cart app. Users add items like ["apple", "banana", ["orange", ["grape", "kiwi"]]] . Suddenly, your loops break because of those sneaky nested arrays. Frustrating, right? Array flattening turns this mess into a simple ["apple", "banana", "orange", "grape", "kiwi"] . In this blog, we'll demystify nested arrays, explore why flattening matters, break down approaches step-by-step, and tackle real interview scenarios—including a custom polyfill you can steal (or improve). What Are Nested Arrays? Nested arrays are arrays containing other arrays as elements within it. Original Nested Array: [ 1 , [ 2 , 3 ], [ 4 , [ 5 , 6 ], 7 ], 8 ] Enter fullscreen mode Exit fullscreen mode Think of it like a filing cabinet: top-level folders hold documents and sub-folders. Why Flatten Arrays win in Real-world scenarios? Flattening simplifies data for: Iteration : Loop once without if (Array.isArray(item)) checks. Processing : Easier sorting, filtering, or mapping on flat lists.…