Katbin

function Node(val) {
  this.val = val;
  this.left = null;
  this.right = null;
}

class BST {
  constructor(val) {
    this.root = new Node(val);
  }

  add(val) {
    let newNode = new Node(val);

    function findPosAndInsert(currNode, newNode) {
      if (newNode.val < currNode.val) {
        if (!currNode.left) {
          currNode.left = newNode;
        } else {
          findPosAndInsert(currNode.left, newNode);
        }
      } else {
        if (!currNode.right) {
          currNode.right = newNode;
        } else {
          findPosAndInsert(currNode.right, newNode);
        }
      }
    }

    if (!this.root) {
      this.root = newNode;
    } else {
      findPosAndInsert(this.root, newNode);
    }
  }

  remove(val) {
    let self = this;
    let removeNode = function (node, val) {
      if (!node) {
        return null;
      }
      if (val === node.val) {
        if (!node.left && !node.right) {
          return null;
        }
        if (!node.left) {
          return node.right;
        }
        if (!node.right) {
          return node.left;
        }
        let temp = self.getMinimum(node.right);
        node.val = temp;
        node.right = removeNode(node.right, temp);
        return node;
      } else if (val < node.val) {
        node.left = removeNode(node.left, val);
        return node;
      } else {
        node.right = removeNode(node.right, val);
        return node;
      }
    };
    this.root = removeNode(this.root, val);
  }

  getMinimum(node) {
    if (!node) {
      node = this.root;
    }
    while (node.left) {
      node = node.left;
    }
    return node.val;
  }

  // helper method
  contains(value) {
    let doesContain = false;

    function traverse(bst) {
      if (this.root.value === value) {
        doesContain = true;
      } else if (this.root.left !== undefined && value < this.root.value) {
        traverse(this.root.left);
      } else if (this.root.right !== undefined && value > this.root.value) {
        traverse(this.root.right);
      }
    }

    traverse(this);
    return doesContain;
  }
}

const bst = new BST(4);
bst.add(3);
bst.add(5);
bst.remove(3);
console.log(bst);