Deepest Leaves Sum LeetCode solution in JavaScript

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var deepestLeavesSum = function (root) {
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  let queue = [];
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  queue.push([root, 0]);
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  let sum = 0;
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  let curLevel = 0;
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  let i = 0;
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  while (queue.length - i > 0) {
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    let [node, level] = queue[i];
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    queue[i] = null;
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    i++;
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    if (level > curLevel) {
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      sum = 0;
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      curLevel = level;
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    }
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    sum += node.val;
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    if (node.left != null) queue.push([node.left, level + 1]);
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    if (node.right != null) queue.push([node.right, level + 1]);
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  }
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  return sum;
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  //time: o(n)
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  //space: o(n)
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};