Creating, manipulating and calculating distance between nodes inside a Binary Search Tree

BinarySearchTree.js

function Node(value){
  this.value = value;
  this.left = null;
  this.right = null;
}
function BinarySearchTree() {
  this.root = null;
}

BinarySearchTree.prototype.push = function (val) {

  if(this.root === null) {
    this.root = new Node(val);
  }
  else {
    var currentNode = this.root;
    while (currentNode != null) {
      if (val < currentNode.value) {
        if (currentNode.left == null) {
          currentNode.left = new Node(val);
          break;
        } else {
          currentNode = currentNode.left;
        }
      } else {
        if (currentNode.right == null) {
          currentNode.right = new Node(val);
          break;
        } else {
          currentNode = currentNode.right;
        }
      }
    }

  }
}

function distanceFromNode (node, value) {
  if(node == null) {
  	//if return null it's going to sum with the prior results(in javascript the operation (1+null=1) )
    return undefined;
  }
  if(node.value == value) {
    return 0;
  } else {
    if(value < node.value) {
      return 1+distanceFromNode(node.left,value);
    } else if(value > node.value){
      return 1+distanceFromNode(node.right,value);
    }
  }
}

function findLowestCommonAncestor (node, value1, value2) {
  if(node == null) {
    return null;
  }
  if(node.value > value1 && node.value > value2) {
    return findLowestCommonAncestor(node.left, value1, value2);
  }
  if(node.value < value1 && node.value < value2) {
    return findLowestCommonAncestor(node.right, value1, value2);
  }
  return node;
}

// returns the Distance between two nodes given the root of the Binary Tree and 2 random values
function distanceBetweenTwoNodes(root, value1, value2) {
  var common = findLowestCommonAncestor(root, value1, value2);

  if(common == null || common == undefined) {
    return -1;
  }
  if( distanceFromNode(common,value1) == -1 ) {
    return -1;
  }
  if( distanceFromNode(common,value2) == -1 ) {
    return -1;
  }
  return distanceFromNode(common,value1) + distanceFromNode(common,value2);

}

function distanceBetweenTwoNodes(root, value1, value2) {
  var common = findLowestCommonAncestor(root, value1, value2);

  if(common == null || common == undefined) {
    return -1;
  }
  if( distanceFromNode(common,value1) == -1 ) {
    return -1;
  }
  if( distanceFromNode(common,value2) == -1 ) {
    return -1;
  }
  return distanceFromNode(common,value1) + distanceFromNode(common,value2);

}

function sumFromUpperNodeToLowerNode (upperNode, lowerNode) {
  if (upperNode == null || lowerNode == null ) {
  	//if return null it's going to sum with the prior results(in javascript the operation (1+null=1) )
   return undefined;
  }
  if(upperNode === lowerNode) {
    return lowerNode.value;
  } else {

    if(upperNode.value < lowerNode.value) {
      return upperNode.value + sumFromUpperNodeToLowerNode(upperNode.right,lowerNode);
    } else if(upperNode.value > lowerNode.value){
      return upperNode.value + sumFromUpperNodeToLowerNode(upperNode.left,lowerNode);
    }
  }
}

function findSumBetweenTwoNodes (root, node1, node2) {
  var common = findLowestCommonAncestor(root, node1.value, node2.value);

  if(common == null || common == undefined) {
    return undefined;
  }
  return sumFromUpperNodeToLowerNode(common,node1) +
         sumFromUpperNodeToLowerNode(common,node2) -
         common.value;
}
function findNodeInTree(root, value) {
  if (root == null) {
    return null;
  }
  if(root.value === value) {
    return root;
  } else {
    if(value < root.value) {
      return findNodeInTree(root.left, value);
    } else {
      return findNodeInTree(root.right, value);
    }

  }
}
/*
  Test your code through here(main func)
*/
function testCode() {
  var test = [9,5,7,6,8,4,11,20,3,17,19,1,45,2];
// 9 -> 11 -> 20 -> 45;
// 9 -> 11 -> 20 -> 17 -> 19
// 9 -> 5 -> 4 -> 3 -> 1 -> 2
// 9 -> 5 -> 7 -> 6
// 9 -> 5 -> 7 -> 8

//        9
//     5     11
//   4  7       20
//  3  6  8  17    45
// 1          19
//  2

  var binaryTree = new BinarySearchTree();
  var root = new Node(test[0]);
  binaryTree.root = root;

  for(var i = 1; i < test.length; i++) {
    binaryTree.push(test[i]);
  }
  /* To test DISTANCE between nodes */
  // console.log(distanceBetweenTwoNodes(binaryTree.root,3,8)); //Should return 4
  // console.log(distanceBetweenTwoNodes(binaryTree.root,9,6)); //Should return 3
  // console.log(distanceBetweenTwoNodes(binaryTree.root,9,20)); //Should return 2
  // console.log(distanceBetweenTwoNodes(binaryTree.root,-9,-6)); //Should return -1
  // console.log(distanceBetweenTwoNodes(binaryTree.root,9,-19)); //Should return -1
  // console.log(distanceBetweenTwoNodes(binaryTree.root,3,20)); //Should return 5
  // console.log(distanceBetweenTwoNodes(binaryTree.root,2,19)); //Should return 9

  /* To test SUM between nodes */
  var node1 = findNodeInTree(binaryTree.root, 2);
  var node2 = findNodeInTree(binaryTree.root, 19);
  console.log('node1:',node1);
  console.log('node2:',node2);  
  var sum = findSumBetweenTwoNodes (binaryTree.root, node1, node2);
  console.log('result SUM: ',sum); //should return 91
}
//running the main func to test the code...
testCode();