Find Largest Value in Each Tree Row LeetCode solution in JavaScript

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var largestValues = function (root) {
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  if (!root) return [];
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  const op = [];
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  const Q = [[root, 1]];
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  while (Q.length) {
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    const [r, l] = Q.shift();
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    if (op.length < l) op.push(-Infinity);
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    op[l - 1] = Math.max(op[l - 1], r.val);
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    if (r.left) Q.push([r.left, l + 1]);
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    if (r.right) Q.push([r.right, l + 1]);
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  }
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  return op;
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};