Implement Array.prototype.flat with Depth Parameter

Problem Statement

Implement a function `flatten(arr, depth = 1)` that flattens nested arrays recursively up to the specified depth limit without using native `Array.prototype.flat()`.

Target Complexity

Time:

O(N) where N is total items in all sub-arrays

Space:

O(D) call stack depth

Interview Talking Points:

• Explain recursive vs iterative stack-based approaches to avoid call stack overflow on 10,000+ nested arrays.
• Discuss Array.prototype.reduce vs for...of loop performance in V8.

Solution Editor (JavaScript)

Ready to run

Test Results

Flattens 1 level by default

Test #1

Flattens all levels with Infinity depth

Test #2