House Robber III LeetCode solution in JavaScript

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var rob = function (root) {
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  const dfs = (node = root) => {
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    if (!node || node.val === null) return [0, 0];
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    const { val, left, right } = node;
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    const [robL, notRobL] = dfs(left);
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    const [robR, notRobR] = dfs(right);
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    const rob = val + notRobL + notRobR;
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    const notRob = Math.max(robL, notRobL) + Math.max(robR, notRobR);
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    return [rob, notRob];
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  };
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  return Math.max(...dfs());
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};