2625. Flatten Deeply Nested Array

Given a multi-dimensional array arr and a depth n, return a version of the array flattened to that depth. Do not use Array.prototype.flat().

📄 Problem Statement

A multi-dimensional array contains integers or other nested arrays. Flattening means replacing those nested arrays with their elements.

Flatten only up to the given depth n.
The initial array has depth 0. Nested elements increase in depth as you go deeper.
You must not use the built-in flat() method.

💡 Example


arr = [1, [2, [3, [4]], 5]]
n = 1
// ➞ [1, 2, [3, [4]], 5]

n = 2
// ➞ [1, 2, 3, [4], 5]

n = 3
// ➞ [1, 2, 3, 4, 5]

🧠 Explanation

Recursively loop through the array. For each element:

If it’s an array and depth is not yet exhausted, flatten it one level deeper.
Otherwise, push it to the result as-is.

Keep track of the current depth and stop when it equals the specified limit.

✅ Your Solution


/**
 * @param {Array} arr
 * @param {number} depth
 * @return {Array}
 */
function flat(arr, depth) {
    const result = [];

    for (const item of arr) {
        if (Array.isArray(item) && depth > 0) {
            result.push(...flat(item, depth - 1));
        } else {
            result.push(item);
        }
    }

    return result;
}