AVL Tree in JavaScript

avl_tree.js

class BinaryTreeNode {
  constructor(value) {
    this.value = value;
    this.left = null;
    this.right = null;
  }

  depth() {
    let result = 0;
    if (this.left) {
      result = Math.max(result, this.left.depth() + 1);
    }
    if (this.right) {
      result = Math.max(result, this.right.depth() + 1);
    }
    return result;
  }
}

class AVLTreeNode extends BinaryTreeNode {
  constructor(value) {
    super(value);
  }

  rotateLeft() {
    const B = this, A = B.right;
    B.right = A.left;
    A.left = B;
    return A;
  }

  rotateRight() {
    const A = this, B = A.left;
    A.left = B.right;
    B.right = A;
    return B;
  }

  __insert(value) {
    if (this.value == value) {
      return 0;
    }

    if (value < this.value) {
      if (this.left) {
        this.left = this.left.__insert(value);
      } else {
        this.left = new AVLTreeNode(value);
      }

      const rightDepth = this.right ? this.right.depth() : 0;
      console.log('L', this.value, this.left.depth(), rightDepth);
      if (this.left.depth() - rightDepth > 0) {
        return this.rotateRight();
      } else {
        return this;
      }
    } else { // value > this.value
      if (this.right) {
        this.right = this.right.__insert(value);
      } else {
        this.right = new AVLTreeNode(value);
      }

      const leftDepth = this.left ? this.left.depth() : 0;
      console.log('R', this.value, this.right.depth(), leftDepth);
      if (this.right.depth() - leftDepth > 0) {
        return this.rotateLeft();
      } else {
        return this;
      }
    }
  }

  __show(depth = 0) {
    let s = '  '.repeat(depth) + this.value + "\n";
    if (this.left) {
      s += this.left.__show(depth + 1);
    }
    if (this.right) {
      s += this.right.__show(depth + 1);
    }
    return s;
  }
}

class AVLTree {
  constructor() {
    this.root = null;
  }
  
  insert(value) {
    if (!this.root) {
      this.root = new AVLTreeNode(value);
      return this;
    }

    this.root = this.root.__insert(value);
    return this;
  }

  show() {
    if (!this.root) {
      return 'empty';
    }
    return this.root.__show();
  }
}

const tree = new AVLTree();
for (let i = 1; i <= 100; ++i) {
  tree.insert(i);
}
console.log(tree.show());