Flatten a Nested Array

📌 Definition:

📖 Detailed Explanation:

Modern JS has Array.prototype.flat(depth). For arbitrary depth use flat(Infinity). To implement it yourself, use recursion or a stack; reduce with concat is the classic recursive one-liner.

💻 Solutions:

• JavaScript

const flatten = (arr) => arr.flat(Infinity);

// Manual recursive implementation:
function flattenDeep(arr) {
  return arr.reduce(
    (acc, x) => acc.concat(Array.isArray(x) ? flattenDeep(x) : x),
    []
  );
}

🔑 Key Points:

• arr.flat(Infinity) flattens any depth
• Manual version: reduce + concat + recursion
• Array.isArray(x) decides recurse vs push
• Iterative stack version avoids deep recursion limits

🌍 Real-World Example: