BST.js

class BinaryNode {
  constructor(number) {
    this.number = number;
    this.left = null;
    this.right = null;
  }
}


class BinarySearchTree {
  constructor(number) {
    this.root = new BinaryNode(number);
  }

  insert(number) {
    const newNode = new BinaryNode(number);
    this.insertNode(this.root, newNode);
  }

  insertNode(existingNode, newNode) {
    if (newNode.number <= existingNode.number) {
      if (!existingNode.left) {
        existingNode.left = newNode;
      } else {
        this.insertNode(existingNode.left, newNode);
      }
    } else {
      if (!existingNode.right) {
        existingNode.right = newNode;
      } else {
        this.insertNode(existingNode.right, newNode);
      }
    }
  }

  remove(number) {
    this.root = this.removeNode(this.root, number)
  }

  removeNode(node, target) {

    if (!node) {
      return null;
    }

    if (target < node.number) {
      node.left = this.removeNode(node.left, target);
    }
    else if (target > node.number) {
      node.right = this.removeNode(node.right, target);
    } else {
      if (!node.left && !node.right) {
        node = null;
      } else if (!node.left || !node.right) {
        node = node.right ? node.right : node.left
      } else {
        const candidate = this.findIdealReplacement(node.right);
        node.number = candidate.number;
        node.right = this.removeNode(node.right, candidate.number);
      }
    }
    return node;
  }

  findIdealReplacement(startingNode) {
    if (!startingNode.left)
      return startingNode;
    else
      return this.findIdealReplacement(startingNode.left);
  }

}


testBST = new BinarySearchTree(28)
testBST.insert(21)
testBST.insert(100)
testBST.insert(120)
testBST.insert(110)
testBST.insert(5)
testBST.insert(25)
 console.log(testBST)
testBST.remove(28)
console.log(testBST)