Balanced Binary Tree LeetCode solution in JavaScript

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/**
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 * Definition for a binary tree node.
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 * function TreeNode(val, left, right) {
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 * this.val = (val===undefined ? 0 : val)
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 * this.left = (left===undefined ? null : left)
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 * this.right = (right===undefined ? null : right)
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 * }
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 */
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/**
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 * @param {TreeNode} root
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 * @return {boolean}
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 */
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var isBalanced = function (root) {
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  let result = true;
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  function Dfs(root) {
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    if (!root) return 0;
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    let left = Dfs(root.left);
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    let right = Dfs(root.right);
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    if (Math.abs(left - right) > 1) {
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      result = false;
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      return;
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    }
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    return 1 + Math.max(left, right);
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  }
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  Dfs(root);
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  return result;
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};