94. 二叉树中序遍历/Binary Tree Inorder Traversal

/**
 * 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
 * @return {number[]}
 */
var inorderTraversal = function(root) {
    var result = [];
    var curr = root;

    function traver(node) {
        if (node) {
            traver(node.left);
           if (node.val !== null) {
                result.push(node.val);
            }

            traver(node.right);
        }

    }

    traver(curr);

    return result;
};