Kth Ancestor in Binary Tree using JavaScript

class TreeNode {
    constructor(value = 0, left = null, right = null) {
        this.value = value;
        this.left = left;
        this.right = right;
    }
}

function kthAncestor(root, node, k) {
    let parentMap = new Map();  
    let depthMap = new Map();   

    function buildMaps(node, parent = null, depth = 0) {
        if (node !== null) {
            parentMap.set(node, parent);
            depthMap.set(node, depth);
            buildMaps(node.left, node, depth + 1);
            buildMaps(node.right, node, depth + 1);
        }
    }

    buildMaps(root);

    let ancestor = node;

    while (k > 0 && ancestor !== null) {
        ancestor = parentMap.get(ancestor);
        k--;
    }

    return ancestor ? ancestor.value : null;
}

let root = new TreeNode(1,
    new TreeNode(2, new TreeNode(4), new TreeNode(5)),
    new TreeNode(3, null, new TreeNode(6))
);

let node = root.left.right;
console.log(kthAncestor(root, node, 2));