Search in a Binary Search Tree

# 700. Search in a Binary Search Tree

You are given the root of a binary search tree (BST) and an integer val.

Find the node in the BST that the node’s value equals val and return the subtree rooted with that node. If such a node does not exist, return null.

### Example 1:
```
Input: root = [4,2,7,1,3], val = 2
Output: [2,1,3]
```

### Example 2:
```
Input: root = [4,2,7,1,3], val = 5
Output: []
 ```

Constraints:
```
The number of nodes in the tree is in the range [1, 5000].
1 <= Node.val <= 107
root is a binary search tree.
1 <= val <= 107
```

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} val
 * @return {TreeNode}
 */
 var searchBST = function(root, val) {
    let out = null;
    const search = (node) => {
        if (!node) {
            return null;
        }
        if (node.val === val) {
            out = node;
            return;
        }
        search(node.left);
        search(node.right);
    };

    search(root);
    return out;
};