Here's my solution with maxDepth: function flatten(arr, maxDepth=Infinity, currDepth = 1){ let res = [] for (let i = 0; i < arr.length; i++) { if (!Array.isArray(arr[i]) || currDepth > maxDepth) { res.push(arr[i]) } else { res = res.concat(flatten(arr[i], maxDepth, ++currDepth)) } } return res }