Count Nodes Equal to Average of Subtree LeetCode solution in JavaScript

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var averageOfSubtree = function (root) {
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  let result = 0;
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  const traverse = (node) => {
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    if (!node) return [0, 0];
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    const [leftSum, leftCount] = traverse(node.left);
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    const [rightSum, rightCount] = traverse(node.right);
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    const currSum = node.val + leftSum + rightSum;
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    const currCount = 1 + leftCount + rightCount;
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    if (Math.floor(currSum / currCount) === node.val) result++;
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    return [currSum, currCount];
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  };
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  traverse(root);
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  return result;
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};