```js
var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
function Node(value) {
this.value = value;
this.left = null;
this.right = null;
}
function BinarySearchTree() {
this.root = null;
}
function isBinarySearchTree(tree) {
// change code below this line
// change code above this line
}
```
### After Test
```js
BinarySearchTree.prototype.push = function(val) {
var root = this.root;
if (!root) {
this.root = new Node(val);
return;
}
var currentNode = root;
var newNode = new Node(val);
while (currentNode) {
if (val < currentNode.value) {
if (!currentNode.left) {
currentNode.left = newNode;
break;
} else {
currentNode = currentNode.left;
}
} else {
if (!currentNode.right) {
currentNode.right = newNode;
break;
} else {
currentNode = currentNode.right;
}
}
}
};
```
## Solution