Tree - DFS preorder

get-values-method.js

getValues() {
    let result = [];

    function traverse(node) {
      result.push(node.value);

      if (node.left) {
        traverse(node.left);
      }
      if (node.right) {
        traverse(node.right);
      }
    }
    traverse(this);

    return result;
  }