Binary tree inorder traversal [https://leetcode.com/problems/binary-tree-inorder-traversal/]

binary_tree_inorder_traversal.js

/**
 * 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) {
    const result = [];

    getNodeValues(root, result);

    return result;
};

var getNodeValues = function(node, result) {
    if (!node) {
        return;
    }

    if (node.left) {
        getNodeValues(node.left, result);
    }

    result.push(node.val);

    if (node.right) {
        getNodeValues(node.right, result);
    }
}