[js] [Symbol.iterator] is solution
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```javascript []\n/**\n * @param {Array} arr\n * @param {number} depth\n * @return {Array}\n */\nvar flat = function (arr, n) {\n    const stack = [[arr[Symbol.iterator](), n]]\n    const result = []\n\n    while (stack.length) {\n        const [iterator, depth] = stack.pop()\n\n        for (let el of iterator) {\n            if (Array.isArray(el) && depth > 0) {\n                stack.push([iterator, depth], [el[Symbol.iterator](), depth - 1])\n\n                break\n            } else {\n                result.push(el)\n            }\n        }\n    }\n\n    return result;\n};\n```
['JavaScript']