Implement a binarySearchTree class with the following properties:

• A .left property, a binary search tree (BST) where all values are lower than than it the current value.

• A .right property, a BST where all values are higher than than it the current value.

• A .insert() method, which accepts a value and places in the tree in the correct position.

• A .contains() method, which accepts a value and returns a boolean reflecting whether or not the value is contained in the tree.

• A .depthFirstLog() method, which accepts a callback and executes it on every value contained in the tree.

  var BinarySearchTree = function (value) {
    this.left;
    this.right;
    this.value = value;
  };
  
  BinarySearchTree.prototype.insert = function (value) {
    var newNode = new BinarySearchTree(value);
    var searchTree = function (node) {
      if (!node.left && node.value > value) {
        node.left = newNode;
      } else if (!node.right && node.value < value) {
        node.right = newNode;
      } else if (node.left && node.value > value) {
        searchTree(node.left);
      } else if (node.right && node.value < value) {
        searchTree(node.right);
      }
    };
  
    searchTree(this);
  };
  
  BinarySearchTree.prototype.contains = function (value) {
    var contains = false;
    var searchTree = function (node) {
      if (node.value === value) { contains = true; }
      if (!contains && node.left) { searchTree(node.left); }
      if (!contains && node.right) { searchTree(node.right); }
    };
  
    searchTree(this);
    return contains;
  };
  
  BinarySearchTree.prototype.depthFirstLog = function (cb) {
    var depthLog = function (node) {
      cb(node);
  
      if (node.left) { depthLog(node.left); }
      if (node.right) { depthLog(node.right); }
    };
  
    depthLog(this);
  };