AVL Tree class in Javascript

Here is the complete implementation of the AVL Tree Class −

Example

class AVLTree {    constructor() {       // Initialize a root element to null.       this.root = null;    }    getBalanceFactor(root) {       return this.getHeight(root.left) - this.getHeight(root.right);    }    getHeight(root) {       let height = 0;       if (root === null || typeof root == "undefined") {          height = -1;       } else {          height = Math.max(this.getHeight(root.left), this.getHeight(root.right)) + 1;       }       return height;    }    insert(data) {       let node = new this.Node(data);       // Check if the tree is empty       if (this.root === null) {          // Insert as the first element this.root = node;       } else {          insertHelper(this, this.root, node);       }    }    inOrder() {       inOrderHelper(this.root);    } } AVLTree.prototype.Node = class {    constructor(data, left = null, right = null) {       this.data = data;       this.left = left;       this.right = right;    } }; function insertHelper(self, root, node) {    (root === null) {       root = node;    } else if (node.data < root.data) {       // Go left!       root.left = insertHelper(self, root.left, node);       // Check for balance factor and perform appropriate rotation       if (root.left !== null && self.getBalanceFactor(root) > 1) {       if (node.data > root.left.data) {          root = rotationLL(root);       } else {          root = rotationLR(root);       }    } } else if (node.data > root.data) {    // Go Right! root.    right = insertHelper(self, root.right, node);    // Check for balance factor and perform appropriate rotation    if (root.right !== null && self.getBalanceFactor(root) < -1) {       if (node.data > root.right.data) {          root = rotationRR(root);       } else {          root = rotationRL(root);       }    } } return root; } function inOrderHelper(root) {    if (root !== null) {       inOrderHelper(root.left);       console.log(root.data);       inOrderHelper(root.right);    } } function rotationLL(node) {    let tmp = node.left;    node.left = tmp.right;    tmp.right = node;    return tmp; } function rotationRR(node) {    let tmp = node.right;    node.right = tmp.left;    tmp.left = node;    return tmp; } function rotationLR(node) {    node.left = rotationRR(node.left);    return rotationLL(node); } function rotationRL(node) {    node.right = rotationLL(node.right);    return rotationRR(node); }