Average of Levels in Binary Tree LeetCode solution in JavaScript

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var averageOfLevels = function (root) {
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  let avg = [root.val];
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  let level = [];
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  let queue = [root];
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  while (queue.length > 0) {
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    let curr = queue.shift();
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    if (curr.left) {
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      level.push(curr.left);
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    }
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    if (curr.right) {
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      level.push(curr.right);
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    }
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    if (queue.length === 0) {
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      queue.push(...level);
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      avg.push(level.reduce((a, b) => a + b.val, 0) / level.length);
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      level = [];
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    }
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  }
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  avg.pop();
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  return avg;
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};